Scroll compressor with axially biased scroll

ABSTRACT

The pressure of a discharged refrigerant gas introduced into a rotary scroll (18) in the portion opposing a compression chamber is utilized to urge the rotary scroll (18) toward the compression chamber so as to maintain the axial directional gap of the compression chamber at a small value. A tip seal (98) is disposed while allowing a small gap for a spiral tip seal groove (98) formed at only the front portion of a rotary scroll wrap (18a) so that the rotary scroll (18) is pushed toward a fixed scroll (15) by the urged pressure of the discharged refrigerant gas introduced into a back pressure chamber (39) of the rotary scroll (18). As a result, enlargement of the axial directional gap of the compression chamber is prevented. Therefore, the axial directional gap between the front portion of the spiral wrap of the rotary scroll (18) and the fixed scroll (15), which will easily generate a leakage of a compressed gas due to the deviation of the combination of the parts of the two scrolls, can be assuredly sealed by the tip seal (98a). A small gap (substantially no gap) can be easily secured in the axial directional gap between the front portion of the spiral wrap of the fixed scroll (15) and the rotary scroll (18). Therefore, it can be sealed without a tip seal so that the operation can be continued while reducing the compression leakage at the time of the normal operation.

TECHNICAL FIELD

The present invention relates to supply of oil to a bearing portion of ascroll compressor, a fluid path relating to it and passing through theback side portion of a scroll member and an apparatus for reducing anexcessively compressed load generated due to the fluid and the fluidpath.

BACKGROUND ART

A scroll compressor possessing low vibration and noise characteristicsis arranged in such a manner that a suction chamber is disposed on theouter portion thereof, a discharge port is formed at the central portionof the spiral and the compressed fluid flows in a single direction.Therefore, a discharge valve for compressing the fluid, which has beenconventionally provided for a reciprocating type compressors or a rotarytype compressors, can be eliminated from the structure, and a constantcompression ratio can be realized. Furthermore, the discharge pulsationcan be reduced depending upon the operational conditions of thecompressor and a necessity of having a large discharge space can beeliminated. Therefore, the development and application of the scrollcompressor to a variety of fields in terms of the practical use havebeen made.

However, since its compression chamber must have a multiplicity ofsealing portions, it suffers from an excessively large leakage quantityof the compressed fluid. In particular, it is necessary for a smalldischarge capacity type scroll compressor for use as a home airconditioning refrigerant compressor to extremely improve the dimensionalaccuracy of the spiral portion in order to minimize the gap in thecompression portion from which the leakage will take place. However, thecomplicated shapes of the parts and the dimensional deviations of thespiral portion raise the cost of the scroll gas compressor, and uniformperformance cannot easily be realized. In particular, the gas leakagecannot be easily prevented when the compressor is being operated at lowspeed because of the too long compression time. Therefore, there arisesa problem that the compression efficiency is unsatisfactory incomparison to that obtainable from the reciprocating type compressorsand the rotary type compressor.

In order to overcome the above-described problems, the dimensionalaccuracy of the spiral portion is made to be at a proper level and thecompression efficiency is improved by the oil film seal effect byutilizing lubricating oil in order to prevent the gas leakage which willtake place during the compression operation. As disclosed in JapanesePatent Laid-Open No. 57-8386, a proper quantity of lubricating oil isinjected into the compression chamber, which is performing thecompression operation, so as to seal the gaps of the compression chamberwith the film of the lubricating oil so as to overcome theabove-described problems.

In particular, the scroll refrigerant compressors have been put intopractical use in a refrigerating and air conditioning fields. Therefore,medium to large size compressors such as a package air conditioner and atiller unit and the like having a relatively large refrigerant capacityper one suction process have been already mass-produced.

FIG. 1 illustrates a structure arranged for the purpose of reducing thefluid leakage from the compressor chamber in such a manner that fluid ofan intermediate pressure level introduced from outside the compressorvia a fluid path 1130 is urged against the back side of a rotary scroll1130 so as to push the rotary scroll 1130 toward a fixed scroll 1110.Furthermore, spiral seal members 1117, 1118 (1145, 1180) urged bysprings 1170 and 1181 are fastened to a spiral groove 1146 (see FIGS. 2and 3) formed at the front portions of the spiral wraps 1132 and 1116 ofthe two scrolls. As a result, the portion between a surface 1133 of anend plate 1131 of the rotary scroll 1130 and the front portion of a wrap1116 of the fixed scroll 1110 and a portion between a surface 1136 of anend plate 1111 of the fixed scroll 1110 and a front portion 1149 of alap 1132 of the rotary scroll 1130 are respectively sealed(specification of U.S. Pat. No. 3,994,636).

However, the structure arranged as shown in FIG. 1 in such a manner thatthe seal members 1117 and 1118 are fastened to the corresponding frontportions of the two wraps 1132 and 1116 of the corresponding rotaryscroll 1130 and the fixed scroll 1110 so as to axially seal thecompression chamber encounters a problem in that the compressor will bedamaged by the abnormal pressure rise generated due to the continuousliquid compression taking place in the compression chamber because theseal members 1117 and 1118 disposed at the two end portions prevent thecancellation of the sealing the compression chamber when the rotaryscroll 1130 separates from the fixed scroll 1110 in the axial directiondue to the generation of the liquid compression, which takes place inthe compression chamber, to cancel the sealing of the compressionchamber in the axial direction.

Accordingly, an object of a first invention of this application is toquickly leak the compressed fluid through an axial gap of thecompression chamber so as to instantaneously lower the pressure when anabnormal pressure rise takes place in the compression chamber.

An object of a second invention is to provide a start load reductiondevice capable of reducing the start load of the compressor andimproving the compression efficiency immediately after the start of theoperation.

An object of a third invention is to provide a compressor exhibitingexcellent durability of the sliding portion thereof and capable ofeliminating vibrations and noise at the initial stage of the start ofthe operation by reducing the start load of the compressor and bygradually shifting the operation to the full compression mode with thelapse of time after the start of the operation.

In order to achieve the above-described objects, a first invention of ascroll compressor according to the present invention is characterized inthat: a rotary scroll is disposed between a body frame supporting adrive shaft and stationarily connected to a fixed scroll and the fixedscroll while allowing a small axial directional movement; a seal memberis disposed while allowing a small gap in a spiral groove formed at onlythe front portion of a spiral wrap of the rotary scroll; the rotaryscroll is pushed toward the fixed scroll by the back pressure urgingforce generated from fluid introduced into a back pressure chamberformed in the rotary scroll in its portion opposing the compressionchamber; and the portion between the front portion of a spiral wrap ofthe fixed scroll and a wrap support disc supporting the wrap of therotary scroll is sealed.

The second invention is characterized in that: compressed fluid in acompressed chamber in the final compression stroke is introduced intothe back side of a thrust bearing which supports a rotary scroll and thethrust bearing is supported by the back pressure urging force.

The third invention is characterized in that: a space present on theback side of a thrust bearing which supports a rotary scroll and acompression chamber at the final compression stroke are allowed tocommunicate with each other; the thrust bearing is supported by the backpressure urging force of compressed fluid introduced from a compressionchamber; and a throttle path is formed at an intermediate position of acommunication path.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a vertical cross sectional view which illustrates aconventional scroll compressor;

FIGS. 2 and 3 are respectively partial cross sectional views whichillustrate the sealed portion of the compression chamber shown in FIG.1;

FIG. 4 is a vertical cross sectional view which illustrates anembodiment of a scroll refrigerant compressor according to the presentinvention;

FIG. 5 is an exploded view which illustrates essential parts of thecompressor;

FIG. 6 is a partial cross sectional view which illustrates a check valveunit disposed in a discharge port portion of the compressor;

FIGS. 7, 8 and 9 are respectively perspective views which illustrateelements of the check valve unit shown in FIG. 6;

FIG. 10 is an perspective exploded view which illustrates small-sizeelements of the compressor;

FIG. 11 is a partial cross sectional view which illustrates a mainbearing portion of the compressor;

FIG. 12 is a perspective view which illustrates seal parts of thecompressor;

FIG. 13 is a partial cross sectional view which illustrates a thrustbearing portion of the compressor;

FIG. 14 is a perspective view which illustrates the thrust bearing shownin FIG. 13;

FIGS. 15 and 16 are respectively cross sectional views which illustratethe operation of a back pressure control valve unit of the compressor;

FIG. 17 is a lateral cross sectional view taken along line XVII--XVII ofFIG. 4;

FIG. 18 is a characteristic graph which illustrates the pressure changeof a refrigerant gas from a suction stroke to a discharge stroke of thecompressor;

FIG. 19 is a characteristic graph which illustrates the pressure changeat a fixed point in each compression chamber;

FIG. 20 is a vertical cross sectional view which illustrates a secondembodiment of the scroll refrigerant compressor according to the presentinvention;

FIGS. 21 and 22 are respectively perspective views which illustrate apartition cap and bearing elements of the compressor;

FIG. 23 is a partial cross sectional view which illustrates a mainbearing portion of the compressor;

FIG. 24 is a partial cross sectional view which illustrates a thrustbearing portion of the compressor;

FIG. 25 is a vertical cross sectional view which illustrates a thirdembodiment of the scroll refrigerant compressor according to the presentinvention;

FIG. 26 is a partial cross sectional view which illustrates a mainbearing portion of the compressor;

FIG. 27 is a perspective view which illustrates a partition plate foruse in a trochoid pump unit shown in FIG. 26;

FIG. 28 is a partial cross sectional view which illustrates a mainbearing portion of a fourth embodiment of the scroll refrigerantcompressor according to the present invention;

FIG. 29 is a perspective view which illustrates the bearing elementsshown in FIG. 28;

FIG. 30 is a perspective exploded view which illustrates elements of anoil supply pump unit of the compressor;

FIG. 31 is a partial cross sectional view which illustrates a mainbearing portion of a fifth embodiment of the scroll refrigerantcompressor according to the present invention;

FIG. 32 is a perspective exploded view which illustrates elements of anoil supply pump unit of the compressor;

FIG. 33 is a perspective view which illustrates bearing elements shownin FIG. 31;

FIG. 34 is a partial cross sectional view which illustrates a mainbearing portion of a sixth embodiment of the scroll refrigerantcompressor according to the present invention;

FIG. 35 is a perspective view which illustrates elements of an oilsupply pump unit of the compressor;

FIG. 36 is a vertical cross sectional view which illustrates a seventhembodiment of the scroll refrigerant compressor according to the presentinvention;

FIG. 37 is a vertical cross sectional view which illustrates an eighthembodiment of the scroll refrigerant compressor according to the presentinvention;

FIG. 38 is a vertical cross sectional view which illustrates a ninthembodiment of the scroll refrigerant compressor according to the presentinvention; and

FIG. 39 is a vertical cross sectional view which illustrates a tenthembodiment of the scroll refrigerant compressor according to the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

A first embodiment of a scroll refrigerant compressor of the presentinvention will now be described with reference to FIGS. 4 to 19.

Referring to FIG. 4, reference numeral 1 represents a sealing case whichis made of iron and the inner portion of which is sectioned into anupper motor chamber 6 and a lower accumulator chamber 46 by a body frame5 which secures, by means of a bolt, a fixed scroll portion 15 to beengaged with a rotary scroll 18 to form a compression chamber and whichsupports a drive shaft 4.

The motor chamber 6, arranged to be under a high pressure atmosphere,has a motor 3 which is disposed in the upper portion thereof and whichis controlled by DC power in such a manner that its rotational speed isvaried, and a compression portion formed in the lower portion thereof.The body frame 5 supporting the drive shaft 4, to which a rotor 3a ofthe motor 3 is connected and fixed, is made of eutectic graphite castiron exhibiting an excellent sliding characteristic and weldability. Aprojecting portion 79a formed on the outer surface of the body frame 5is positioned in contact with the inner surface and the end surface ofeach of an upper sealing case 1a and a lower sealing case 1b. Theprojecting portion 79a, the upper sealing case 1a ant the lower sealingcase 1b are hermetically welded to each other by a common weld bead 79b.

The drive shaft 4 is supported by a main bearing 12, which is disposedet the central portion of an upper bearing 11 disposed on the topsurface of the body frame 5, and a thrust bearing portion 13 which isformed on the top surface of the body frame 5 and has a plurality ofshallow grooves diagonally formed on the same. A crank shaft 14 disposedat the lower end portion of the drive shaft 4 in such a manner that itis positioned eccentrically from the axis of the drive shaft 4 isengaged with a rotary bearing 18b of a rotary boss portion 18e formed ina rotary scroll 18.

A fixed scroll 15 is composed of a fixed scroll wrap 15a, which is madeof a high silicon-aluminum alloy, the coefficient of thermal expansionof which is an intermediate value between that of pure aluminum and thatof eutectic graphite cast iron and which is formed into a spiral shapeas shown in FIG. 17 and an end plate 15b. At the central portion of theend plate 15b, a discharge port 16, which opens at the position at whichthe spiral of the fixed scroll wrap 15a is commenced, is formed in sucha manner that it is allowed to communicate with a discharge path 80which opens in the motor chamber 6. Furthermore, a suction chamber 17 isformed on the outer surface of the fixed scroll wrap 15a.

A check valve unit 50 is fastened to the end plate 15 on the sideopposing the rotary scroll, the check valve unit 50 comprising, as shownin detail in FIGS. 6 to 9, a valve body 50b (or a valve body 50e havinga discontinuous annular hole 50ea) made of a thin steel plate formed bycutting a plurality of the outer portion thereof, a valve case 99 havinga check valve hole 50a, a central hole 50g and a plurality of dischargeapertures 50h formed around the central hole 50g and a spring unit 50cdisposed between the valve body 50b and the valve case 99. The springunit 50c has a shape memory characteristic with which it is contractedwhen its temperature exceeds 50° C. and it is elongated when the same islowered to below 50° C. Therefore, during the operation of thecompressor, the spring unit 50c is contracted to the bottom surface ofthe check valve hole 50a due to the effect of the pressure of thedischarged gas and the shape memory characteristic displayed when thetemperature exceeds 50° C. On the other hand, when the operation of thecompressor is stopped, the spring unit 50c presses the valve body 50against the end plate 15b to close the discharge portion when thetemperature is 50° C. or lower.

As shown in FIGS. 4 and 17, the spiral rotary scroll wrap 18a, which isengaged with the fixed scroll wrap 15a to form the compression chamberand the aluminum alloy rotary scroll 18 on which the rotary boss portion81e, which is engaged with the crank shaft 14 of the drive shaft 4, isstood erect, are surrounded by the fixed scroll 15 and the body frame 5.The surface of a wrap support disc 18c and that of the rotary scrollwrap 18a are respectively subjected to a hardening treatment such asporous nickel plating. A spiral tip seal groove 98 as disclosed in U.S.Pat. No. 3,994,636 is formed at the leading portion of the rotary scrollwrap 18a, the tip seal groove 98 having resin tip seals 98a fitted atsmall intervals secured therebetween.

When the rotary scroll 18 is pressed in the axial direction of the fixedscroll 15, the flat portion of the wrap support disk 18c comes incontact with the leading portion of the fixed scroll wrap 15a. However,the leading portion of the rotary scroll wrap 18a does not come incontact with the fixed scroll 15 while leaving several microns, the gapthus-formed being sealed by the tip seal 98a.

The discharge path 80 comprises: a discharge chamber 2 formed by adischarge cover 2a, which is fastened to the end plate 15b to cover thecheck valve unit 50, and the mirror plate 15b; a gas path 80b formed inthe fixed scroll 15; a gas path 80a formed in the main frame 5; and adischarge chamber 2b formed by a discharge guide 81 fastened to the bodyframe 5 to cover the main bearing 12 and the body frame 5. The gas path80a and the gas path 80b are respectively further symmetrically disposed(see FIG. 17).

A multiplicity of apertures 81a are formed on the upper surface of thedischarge guide 81 in such a manner that they are equally spacedsymmetrically.

The accumulator chamber 46 allowed to communicate with the portionadjacent to an evaporator of the refrigerating cycle is constituted by alower sealing case 1b, the fixed scroll 15 and the body frame 5. Asuction pipe 47 allowed to communicate with the accumulator chamber 46is disposed on the side surface of the lower sealed case 16.Furthermore, suction holes 43 are formed in the two portions of thefixed scroll 15, that is, at the position confronting the suction pipe47 and positions respectively away from the above-described position byan angular degree of about 90°.

A low-pressure oil reservoir 46a formed at the bottom portion of theaccumulator chamber 46 and the suction hole 43 are allowed tocommunicate with each other by means of an oil suction hole 9a formed inthe discharge cover 2a and an oil suction hole 9b formed in the fixedscroll 15 and having a small diameter. The above-described oil suctionholes (9a, 9b) are arranged to be capable of sucking refrigerant liquidor lubricating oil left in the low pressure oil reservoir 46a byutilizing negative pressure which can be generated when the refrigerantgas passes through the suction hole 43.

A thrust bearing 20 formed into a flat plate, the rotational directionalmovement of which is restricted by a parallel pin 19 in the form of asplit cotter pin and only the axial directional movement of which ispermitted, is disposed between the wrap support disc 18c and the bodyframe 5, the thrust bearing 20 being brought into contact with an endplate fastening surface 15b1 disposed between the body frame 5 and thefixed scroll 15 by elastic force of an annular seal ring 70 (made ofrubber) disposed between the thrust bearing 20 and the body frame 5.

The height from an end plate sliding surface 15b2, which slides on thewrap support disc 18c of the rotary scroll 18, to the end platefastening surface 15b1 is arranged to be a value which is larger thanthe thickness of the wrap support disc 18c by about 0.015 to 0.20 mm inorder to improve the sealing effect obtained by means of the oil film inthe sliding portion.

An annular sealing groove 95, which is coaxially disposed with thecentral portion of the rotary bearing 18b, is formed in the rotary bossportion 18e of the rotary scroll 18 on the surface adjacent to the bodyframe 5. An annular ring 94, which is made of teflon possessingflexibility and from which a portion is cut as shown in FIG. 12, isfitted to the above-described annular sealing groove 95 in such a mannerthat the outer surface of the annular ring 94 is positioned in contactwith the side surface of the annular sealing groove 95. The annular ring94 seals a portion between a back pressure chamber 39 of the rotaryscroll 18 formed by the rotary scroll 18, the body frame 5 and thethrust bearing 20 and the main bearing 12 which supports the drive shaft4.

The annular thrust bearing 20 is made of a sintered alloy, in whichthrough holes can easily be formed, the annular thrust bearing 20having, as shown in FIGS. 13 and 14, two guide holes 93 in which splitcotter pins 19 are movably inserted, an annular oil groove 92 and an oilhole 91. The annular thrust bearing 20 is fitted within a thrust ringgroove 90 formed in the body frame 5.

A release gap 27, the size of which is about 0.05 mm, is formed betweenthe body frame 5 and the thrust bearing 20. An annular groove 28 forreceiving a seal ring 70 is formed on the inner and outer sides of therelease gap 27. The seal ring 70 seals the portion between the releasegap 27 and the back pressure chamber 39.

The release gap 27 is allowed to communicate with a third compressionchamber 60 serving as the final compression stroke by means of a thrustback pressure introduction hole 89a formed in the body frame 5 and athrust back pressure introduction hole 89b formed in the fixed scroll15.

A rotation stopping member (hereinafter called an "Oldham's ring") 24disposed on the inside of the thrust bearing 20 and acting to stop therotation of the rotary scroll 18 is made of a light alloy or a fiberreinforced composite material which can be suitably used in thesinter-molding or the inject molding manufacturing process, the rotationstopping member 24 having parallel-key shape key portions formed on thetwo flat sides thereof, the two key portions being formed perpendicularto each other. The key portion formed on the upper side of the rotationstopping member 24 is engaged with the key groove 7 formed in the bodyframe 5, while the key portion formed on the lower side of the same isengaged with the key groove 71a formed in the wrap support disc 18c, torespectively slide.

The thickness of the Oldham's ring 24 is arranged in such a manner thatit is able to smoothly slide between the body frame 5 and the wrapsupport disc 18c via oil films while preventing a jumping phenomenonwhen the Oldham's ring 24 performs the reciprocating motion.

A discharge pipe 31 is fastened to the outer surface of the upper endwall of the upper sealed case 1a, while a glass terminal 88, to which amotor power supply which is allowed to communicate with the DC inverterpower supply is connected, is fastened to the central portion of thesame.

The portion including the discharge pipe 31 and the glass terminal 88and the portion including the motor 3 are separated from each other byan oil separator 87 fastened to the upper sealed case 1a. A rotor 3aaxially positioned by the stepped portion of the drive shaft 4 is,together with an upper balance weight 75 formed by a punching work,fixed to the drive shaft 4 by means of a bolt. The upper balance weight75 is formed into a disc shape, the upper balance weight 75 having adiameter which is larger than the outer diameter of the rotor 3a inorder to efficiently centrifugally separate the lubricating oilcontained in the discharged refrigerant gas.

A shielding plate 86 fastened to the body frame 5 is disposed betweenthe lower balance weight 76 fastened to the lower end portion of therotor 3a and the discharge guide 81 in such a manner that the shieldingplate 86 is positioned adjacently to the lower balance weight 76.

The discharge chamber oil reservoir 34 formed in the lower portion ofthe motor chamber 6 is allowed to communicate with the upper portion ofthe motor chamber 6 by a cooling path 35 formed by cutting a portion ofthe outer surface of the statar 3b of the motor 3.

The discharge chamber oil reservoir 34 is also allowed to communicatewith an oil chamber 78 positioned at an intermediate position betweenthe main bearing 12 and the rotary bearing 18b via an oil hole 38aformed in the body frame 5.

Spiral oil grooves 41a and 41b are respectively formed on the surface ofa sliding shaft portion 4a of the drive shaft 4 and that of the crankshaft 14 in a direction in which lubricating oil in the oil chamber 78ais, in a screw-pump manner, supplied to an oil chamber 78b formed by therotary bearing 18band the crank shaft 14 and to the portion includingthe motor 3 when the drive shaft 4 is forward rotated, the leadingportions of the spiral oil grooves 41a and 41b being arranged to reachthe thrust bearing 13.

The oil chamber 78b and the surface of the main bearing 12 are allowedto communicate with each other by an oil supply hole 73a formed in thedrive shaft 4. An oil reservoir 72 formed between the upper bearing 11and the main bearing 12 and the back pressure chamber 39 are allowed tocommunicate with each other by an oil hole 38b formed in the body frame5 and having a throttle path portion. The end portion of the opening ofthe oil hole 38b adjacent to the back pressure chamber 39 is positionedat a position which is intermittently opened/closed when the annularring 94 rotates together with the rotary scroll 18. A second compressionchamber 51 and the back pressure chamber 39, which are intermittentlyallowed to communicate with the suction chamber 17, are allowed tocommunicate with each other by the oil hole 91, an outer space 37 of thewrap support disc 18c, an oil hole 38c formed in the wrap support disc18c and an injection passage 74 constituted by an injection hole 52having a small diameter. The hole hole 91 formed in the thrust bearing20 and the lower stream of the oil hole 91 are intermittentlyopened/closed by the wrap support disc 18c.

As shown in FIGS. 15 and 16, a back pressure control valve unit 25 forcontrolling the pressure of the back pressure chamber 39 is fastened tothe wrap support disc 18c.

The back pressure control valve unit 25 is constituted by astepped-shape cylinder 26 composed of a large-diameter cylinder 26a anda small-diameter cylinder 26b and disposed in the radial direction ofthe wrap support disc 18c, a stepped-shape plunger 29 which is movablein the above-described cylinder, a cap 32 for covering a portion of anopening formed in the cylinder 26 adjacent to the outer space 37, a coilspring 53 disposed between the cap 32 and the plunger 29 and urging theplunger 29 toward the crank shaft 14, an oil hole 54a for establishing acommunication between the portion of the large-diameter cylinder 26aadjacent to the crank shaft 14 and the suction chamber 17 and oil holes54b and 54c for establishing communication between the portion of thesmall-diameter cylinder 26b adjacent to the crank shaft 14 and the oilchamber 78b and the back pressure chamber 39. The operation is arrangedin such a manner that, when the pressure of the back pressure chamber 39is in a proper pressure range, the small-diameter end surface of theplunger 29 closes the end portion of the opening of the oil hole 54badjacent to the cylinder. When the pressure of the back pressure chamber39 is insufficient, the plunger 29 is moved toward the outer space 37due to the difference in the urging force acting to the two sides of theplunger 29 while making the large diameter portion of the plunger 29 tobe the boundary. As a result, the end portion of the opening of the oilhole 54b adjacent to the cylinder is opened, causing the oil chamber 78band the back pressure chamber 39 to be allowed to communicate with eachother. In order to realize the above-described operation, the urgingforce of the coil spring 53 and the dimensions of the cylinder areestablished.

Reference numeral 55 represents an O-ring fastened to the small-diametercylinder 26b for the purpose of sealing the outer surface of thesmall-diameter portion of the plunger 29.

Referring to FIG. 18, the axis of the abscissa stands for the rotationalangle of the drive shaft 4, while the axis of ordinate stands for thepressure of the refrigerant so that it shows the change in the pressureof the refrigerant gas in the suction, the compression and the dischargeprocesses, where a continuous line 62 designates the change in thepressure at the time of the operation with normal pressure and a dashedline designates the change in the pressure at the time of the abnormalrise of the pressure.

Referring to FIG. 19, the axis of abscissa stands for the rotationalangle of the drive shaft 4 and the axis of ordinate stands for thepressure of the refrigerant, where a continuous line 64 designates thechange in the pressure at the openings of the injection holes 52a and52b of second compression chambers 51a and 51b which are not allowed tocommunicate with the discharge chamber 2 and the suction chamber 17 anda dashed line 65 designates the change in the pressure at fixed pointsof first compression chambers 61a and 61b (see FIG. 10) which areallowed to communicate with the suction chamber 17, where line 67 withan alternate long and two short dashes line designates the change in thepressure at fixed points between the first compression chambers 61a and61b and the second compression chambers 51a and 51b and double dashedline designates the change in the pressure of the back pressure chamber39.

FIG. 20 is a vertical cross sectional view which illustrates a secondembodiment of the scroll refrigerant compressor according to the presentinvention. A partition cap 101 formed into a shape shown in FIG. 21 andmade by forming a steel plate is press-fit into a stepped inner wall ofa high pressure oil hole 278a allowed to communicate with the dischargechamber oil reservoir 34 via an oil hole 238a formed in a body frame205, the partition cap 101 being disposed to cover a flange portion 102of a drive shaft 204 as shown in FIG. 23. The partition cap 101 has acut portion 101a formed in a portion thereof and partitions the oilchamber 278a into a portion adjacent to the main bearing 212 and aportion adjacent to the rotary bearing 218bin such a manner that itcloses the cut portion 101a while being fastened to the stepped innerwall of the oil chamber 278a.

A rotary bearing 218, the outer shape of which is arranged to be asshown in FIG. 22, is press-fit into a rotary boss portion 218e of arotary scroll 218. The rotary bearing 218 formed into a cylindricalshape has an outer surface a portion of which is subjected to aflattening work to nave step C of about 100 microns. The portion of thestep C forms a throttle path 103 when press-fit into the rotary bossportion 218e as shown in FIG. 23.

The rotary boss portion 218e has an annular groove 104 and an oil hole105 having a small diameter.

The discharge chamber oil reservoir 34 and a back pressure chamber 239are allowed to communicate with each other via the oil hole 238a, theoil chamber A 278a, a spiral oil groove 241b, an oil chamber 278b, thethrottle path 103, the annular groove 104 and the oil hole 105.

As shown in FIG. 24, the position of a shallow groove 239 is establishedin such a manner that the outer space 37 and the back pressure chamber239 are allowed to communicate with each other via a shallow groove 239formed in the surface of a thrust bearing 219 only when the compressionchamber is at the rotary angle of the suction stroke and they are cutoff by a wrap support disc 218c of the rotary scroll 218 When thecompression chamber is at the rotary angle of the compression stroke.

The other structures are the same as those shown in FIG. 4.

FIG. 25 is a vertical cross sectional view which illustrates a thirdembodiment of the scroll refrigerator compressor according to thepresent invention. Similarly to the case shown in FIG. 20, the partitioncap 101 made by forming a steel plate is, as shown in FIG. 26, press-fitinto a stepped inner wall of a high pressure oil hole 378a allowed tocommunicate with the discharge chamber oil reservoir 34 via an oil hole338a formed in a body frame 305, the partition Cap 101 being disposed tocover the flange portion 102 of a drive shaft 304 similarly to the caseshown in FIG. 23. As a result, the oil chamber 378a is partitioned intoa main bearing portion 312 and a rotary bearing portion 318b.

A rotary bearing 318 is press-fit into a rotary boss portion 318e of arotary scroll 318, the bottom portion of the rotary boss portion 318ehaving a trochoid pump unit 106 fastened thereto and composed of anouter rotor 106a and an inner rotor 106b.

The trochoid pump unit 106 is connected to a drive end shaft 107disposed at the front portion of a crank 314 disposed at an end portionof the drive shaft 304 so as to be operated. The crank shaft 314 and thedrive end shaft 107 are arranged to be concentrically disposed.

A partition plate 110 having a suction hole 108 and a central hole 109formed as shown in FIG. 27 is fastened and secured to a position betweenthe rotary bearing 318b and the trochoid pump unit 106.

An oil groove 111 formed in the central portion of a wrap support disc318c of the rotary scroll 318 serves as a discharge port of the trochoidpump unit, the oil groove 111 and the sliding surface of a main bearing312 being allowed to communicate with each other by an axial directionaloil hole 112 and a radial directional oil hole 113 formed in the driveshaft 304.

The discharge chamber oil reservoir 34 and a back pressure chamber 339of the rotary scroll 318 are allowed to communicate with each otherthrough oil hole 38b by an oil supply path passing through the oilchamber 338a, the oil chamber 378a, the spiral oil groove 341b, thesuction hole 108, the trochoid pump unit 106, the oil groove 111, theaxial oil hole 112, the radial directional oil hole 113, a gap in themain bearing 312 and the oil reservoir 72 and another oil supply pathpassing through the oil chamber 378a, the spiral oil groove 341a and theoil reservoir 72.

The other structures are the same as those shown in FIG. 20.

FIG. 28 is a vertical cross sectional view which illustrates a portionincluding the oil supply pump unit disposed at the front portion of thedrive shaft of a fourth embodiment of the scroll refrigerant compressoraccording to the present invention. A side plate 114 having a suctioncut portion 114a, the shape of which is as shown in FIG. 30 and a sideplate case 118 having a groove 119 are secured and fastened at a certaininterval to a stepped hole portion of the a main bearing 412 of a bodyframe 405 adjacent to a rotary scroll 418. Elements of a rolling pistontype pump unit composed of an annular piston 115, a partition vane 117,a coil spring 116 are disposed between the side plate 114 and the sideplate case 118.

A rotary bearing 418b having a small-diameter outer portion 418f, theshape of which is as shown in FIG. 29, is press-fitted and secured intoa rotary boss portion 418e of a rotary scroll 418. The inner surface ofthe rotary bearing 418b is engaged with a crank shaft 414 of a driveshaft 404 so as to be slid in the same, and the small-diameter outerportion 418f is engaged with the inner surface of the piston 115 so asto be slid in the same.

An oil chamber 478a allowed to communicate with the discharge chamberoil reservoir 34 via an oil hole 438a formed in the body frame 405 iscut off from a back pressure chamber 439 of the rotary scroll 418 by theside plate case 118 press-fit into the body frame 405 and the annularring 94 fastened to the end portion of the rotary boss 418e.

The side plate 114 is positioned in contact with an end surface 404a ofthe stepped portion of the drive shaft 404 so as to cut off the portionadjacent to the oil hole 438a and the portion including thecircumferential surface portion of the piston 115.

The oil chamber 478a is allowed to communicate with the back pressurechamber 439 via the rolling piston type oil pump unit 120, a spiral oilgroove 441b formed in the outer surface of the crank shaft 414, an oilchamber 478b formed at the end portion of the crank shaft 414, an axialdirectional oil hole 112a formed in the core portion of the drive shaft404, a spiral oil groove 441a and an oil hole 438b formed in the bodyframe 405. The opening of the oil hole 438b is intermittently closed bythe reciprocating motion of the Oldham's ring 24.

The other structures are the same as those shown in FIG. 25.

FIG. 31 is a vertical cross sectional view which illustrates a portionof a portion including the oil supply pump unit disposed at the frontportion of the drive shaft of the scroll refrigerant compressoraccording to a fifth embodiment of the present invention. Similarly tothe case shown in FIG. 28, a side plate 114b having, as shown in FIG.32, a circular arc shape suction hole 114c and a projecting portion 114dand a side plate case 118a are fastened and secured at a certaininterval in a stepped hole portion of a main bearing 512 of a body frame505 adjacent to a rotary scroll 518. Elements of a rotary cylinderpiston type pump unit comprising an annular shape piston 115a having aprojecting portion 115b and a groove 115c and similarly to a rotarycylinder piston type pump unit disclosed in, for example, JapanesePatent Publication No. 61-57935 are disposed between the side plate 114band the side plate case 118a.

As shown in FIG. 33, a rotary bearing 518b having a small-diameter outerportion 518f is press-fit into a rotary boss portion 518e of a rotaryscroll 518. Therefore, when the rotary scroll 518 performs the rotarymotion, the small-diameter outer portion 518f intermittently comes incontact with an inner surface 115d of the piston 115a. As a result, thepiston 115a performs a rotary and swing motion the diameter of which issmaller than that of the rotary scroll 518 so that a small dischargepump operation is performed.

The projecting portion 115b of the piston 115a acts to stop the rotationof the piston 115a when it is engaged with a cut-out groove 121 formedin the body frame 505.

The side plate 114b is positioned in contact with an end surface 504a ofthe stepped portion of a drive shaft 504 so as to cut off the portionadjacent to an oil hole 538a and the circumferential surface portion ofthe piston 115a.

An oil chamber 578a allowed to communicate with the discharge chamberoil reservoir 34 via an oil hole 538a formed in the body frame 505 iscut off from a back pressure chamber 539 of the rotary scroll 518 by theside plate 114b press-fit into the body frame 505 and the annular ring94 fastened to the end portion of the rotary boss 518e.

The oil chamber 578a is allowed to communicate with the back pressurechamber 539 via a rotary cylinder piston type oil supply pump unit, aspiral oil groove 541b formed in the outer surface of a crank shaft 514,an oil chamber 578b formed at the end portion of the crank shaft 514, anaxial directional oil hole 112b formed in the core portion of the driveshaft 504, a spiral oil groove 541a and an oil hole 538b formed in thebody frame 504. The opening of the oil hole 538b is intermittentlyclosed by the reciprocating motion of the Oldham's ring 24.

The other structures are the same as those shown in FIG. 25.

FIG. 34 is a vertical cross sectional view which illustrates a portionincluding the oil supply pump unit disposed at the front portion of thedrive shaft of the scroll refrigerant compressor according to a sixthembodiment of the present invention. Similarly, to the cases shown inFIGS. 28 and 31, a side plate case 118b and a side plate case 118a are,at a certain interval, fastened and secured to a stepped hole portion ofa main bearing 612 of a main frame 605 adjacent to a rotary scroll 618.Elements of so-called a slide vane type oil supply pump apparatuscomprising two vane grooves 124 and two discharge holes 125 and as wellas constituted by a rotor 122 secured to a drive shaft 604 and two vanes123 fastened to the corresponding vane grooves 124 and reciprocating inthe vane grooves 124 are disposed between the side cases 118a and 118b.

An oil chamber 678a allowed to communicate with the discharge chamberoil reservoir 34 via an oil hole 638a formed in the body frame 605 iscut off from a back pressure chamber 639 of a rotary scroll 618 by theside plate case 118a press-fit into the body frame 605 and the annularring 94 fastened to the end portion of a rotary boss 618e.

The oil chamber 678a is allowed to communicate with the back pressurechamber 639 via the slide vane type oil supply apparatus, a spiral oilgroove 641b formed on the outer surface of a crank shaft 614, an oilchamber 678b formed at the end portion of the crank shaft 614, an axialdirectional oil hole 112c formed in the core portion of the drive shaft604, a spiral oil groove 641a and an oil hole 638b formed in the bodyframe 604. The opening of the oil hole 638b is intermittently closed bythe reciprocating motion of the Oldham's ring 24.

The other structures are the same as those shown in FIG. 25.

FIG. 36 is a vertical cross sectional view of a seventh embodiment ofthe scroll refrigerant compressor. The inside portion of a sealed case701 made of soft iron is, similarly to the case shown in FIG. 4,partitioned into an upper sealed case 701a and a lower sealed case 701b.The inside portion of the upper sealed case 701a serves as a highpressure space for including a motor 703 similarly to the shown in FIG.4. The inside portion of the lower sealed case 701b serves as a lowpressure space allowed to communicate with the lower stream from theevaporator and constitutes an accumulator chamber 746. The upper sealedcase 701a is constituted by a body shell 701a1 for supporting a rotor703b of the motor 703 and an upper shell 701a2 in which a glass terminal88 for establishing a connection with the motor power supply isdisposed. Furthermore, an upper frame 126 for supporting an end portionof the drive shaft 704 is disposed between the above-described twoshells.

The upper frame 126 is made of gray cast iron displaying bad weldabilityand possessing vibration damping characteristic. A projecting portion779a formed on its outer surface is positioned in contact with the innerwalls of the upper shell 701a2 and the body shell 701a1 and their endsurfaces. A single weld bead 779b seals and secures the upper seal 701a2and the body shell 701a1, and as well as it secures the projectingportion 779a of the upper frame 126 in such a manner that it holds theinside portion. That is, the weld bead 779b forms an alloy structurebetween the upper shell 701a2 made of soft iron and the body shell701a1, but no alloy structure is formed with the surface of the upperframe 126 made of the gray cast iron. Therefore, the weld bead 779bsurrounds and secures the portion around the upper frame 126 whilepreventing the influence of the welding distortion.

An upper balance weight 775 and a lower balance weight 776 are fastenedto the upper and lower end portions of a rotor 703a of the motor 703 insuch a manner that the axial movement of the rotor 703a is restricted ina portion between an end portion of the upper frame 126 and the endportion of the body frame 705.

The diameter of a main bearing 712 of the drive shaft 704 supported bythe upper frame 126 and the body frame 705 is arranged to be larger thanthe sum of the diameter of the crank shaft 714 and the quantity which istwo times the crank eccentricity so that the drive shaft 704 can beremoved upward.

The lower surface of the lower balance weight 776 is positioned incontact with a thrust bearing portion 713 at the top end portion of thebody frame 705 so as to support the drive shaft 704 and the rotor 703a.

An oil reservoir 772 in the upper portion of the main bearing 712 isallowed to communicate with a back pressure chamber 739 of a rotaryscroll 718 via an oil hole 738b.

The thrust bearing 20 is, similarly to the case shown in FIG. 4, allowedto communicate with the compression chamber of the final compressionstroke via a gap present between a bolt 710 for fixing a fixed scroll715 to the body frame 705 and a fastening hole and small gaps around thescrew.

The high pressure oil chamber 778a is allowed to communicate with thedischarge chamber oil reservoir 34 via an oil hole 738a.

The discharge chamber 2 formed in the portion of the fixed scroll 715opposing the compression chamber is allowed to communicate with an oilseparation chamber 128 formed in the upper portion of the upper frame126 via a gas path 780b formed in the fixed scroll 715, a gas path 780aformed in a body frame 705 and a discharge bypass pipe 127.

The oil separation chamber 128 is allowed to communicate with adischarge pipe 731 formed in a body shell 701a1 on the outer surface ofa lower motor coil end 130 via a gas hole 129 formed in the upper frame126 and a motor chamber 706. The surface of an upper end shaft 704d ofthe drive shaft 704 supported by the upper frame 126 has a spiral oilgroove 741d formed in a direction in which the lubricating oil separatedfrom the discharge gas in the oil separating chamber 128 is introducedinto the motor chamber 706 by the viscous pumping operation when thedrive shaft 704 forward rotates.

The oil chamber 778a allowed to communicate with the discharge chamberoil reservoir 34 via the oil hole 738a formed in the body frame 705 iscut off from a back pressure chamber 739 of a rotary scroll 718 by theannular ring 94 fastened to the end portion of a rotary boss portion718e of a rotary scroll 718.

The oil chamber 778a is allowed to communicate with the back pressurechamber 739 via a spiral oil groove 741b formed in the outer surface ofthe crank shaft 714, an oil chamber 778b formed in the end portion ofthe crank shaft 714, an axial directional oil hole 112c formed in thedrive shaft 704, a spiral oil groove 741a, an oil reservoir 772 and theoil hole 738b. An end portion of the opening side of the oil hole 738bis intermittently closed by the rotary motion of the annular ring 94.

The other structures are the same as those shown in FIG. 4.

FIG. 37 is a vertical cross sectional view of an eighth embodiment ofthe scroll refrigerant compressor. The inside portion of a sealed case801 made of soft iron is, similarly to the cases shown in FIGS. 4 and36, partitioned into an upper sealed case 801a and a lower sealed case801b by a body frame 805 supporting the drive shaft 704. The insideportion of the upper sealed case 801a serves as a high pressure spacefor including the motor 703. The inside portion of the lower sealed case801b serves as a low pressure space allowed to communicate with thelower stream from the evaporator and constitutes an accumulator chamber846.

The drive shaft 704 for connecting the motor 703 is, similarly to thecase shown in FIG. 36, supported by a main bearing 812 of the body frame805 and the upper frame 126.

The discharge chamber 2 is allowed to communicate with a high pressuremotor chamber 806 via a gas path 880b formed in a fixed scroll 815, agas path 880a formed in the body frame 805 and the discharge chamber 2cformed by the body frame 805 and the discharge guide 81.

A discharge pipe 831 disposed at the top end portion of the upper sealedcase 801a is allowed to communicate with the motor chamber 806 via thegas hole 129 formed in the upper frame 126.

A plurality of coil springs 131 are disposed in the portion adjacent toa thrust bearing 220 opposing the compression chamber, the end surfaceof each of the coil springs being pushed by a discharge guide 881fastened to the body frame 805 to push the thrust bearing 220 to an endplate 815b of the fixed scroll 815.

The portion adjacent to the back side of the thrust bearing 220 isallowed to communicate with the discharge chamber oil reservoir 34 bythe coil spring fastening hole 132 formed in the body frame 805 and theoil introduction hole 133 formed in the discharge guide 881.

A seal ring 70a is fastened to only the inside of the portion adjacentto the thrust bearing 220, while the outer portion of the same is sealedby a fact that the thrust bearing 220 abuts against the end plate 815b.

The other structures are the same as those shown in FIG. 36.

FIG. 38 is a vertical cross sectional view of a ninth embodiment of thescroll refrigerant compressor according to the present invention. Thesecond compression chambers 51a and 51b which are intermittently allowedto communicate with the suction chamber 17 and the outer space 37 of arotary scroll 918 are allowed to communicate with each other by an oilhole 938c formed in an end plate sliding surface 915b2 of a fixed scroll915 and an injection hole 952 having a small diameter.

The oil hole 938c is formed by a throttle path 938d opened in the outerspace 37 and an oil reservoir path 938e allowed to communicate with theinjection hole 952.

The position of the throttle path 938e is arranged in such a manner thatit is allowed to communicate with the outer space 37 only when thesecond compression chambers 51a and 51b, which are intermittentlyallowed to communicate with the suction chamber 17, are performing thesuction stroke (the state of the first compression chambers 61a and 61b)and it is cut off from the outer space 37 by a wrap support disc 918c ofa rotary scroll 918 when the second compression chambers 51a and 51b areperforming the compression stroke.

A back pressure chamber 939 of the rotary scroll 918 and the outer space37 are arranged in such a manner that they are allowed to communicatewith each other via an oil groove 291 formed in the thrust bearing 220only when the second compression chambers 51a and 51b, which areintermittently allowed to communicate with the suction chamber 17, areperforming the suction stroke (the state of the first compressionchambers 61a and 61b) and they are cut off by the wrap support disc 918cof the rotary scroll 918 when the second compression chambers 51a and51b are performing the compression stroke.

The oil groove 291 formed in the thrust bearing 220 and an opening ofthe oil hole 938 formed in the fixed scroll 915 toward the end platesliding surface 915b2 are formed to confront each other with respect tothe central portion of the rotary scroll 918.

The other structures are the same as those according to the first andsecond embodiments shown in FIGS. 4 to 19 and 20 to 24.

FIG. 39 is a vertical cross sectional view of a tenth embodiment of thescroll refrigerant compressor according to the present invention. Theinside portion of a sealed case 2001 is a high pressure space having, inthe lower portion thereof, a discharge chamber oil reservoir 2034 and ascroll compression mechanism portion and, in the upper portion thereof,the motor 3.

The suction chamber 17 is allowed to directly communicate with the lowpressure side on the outer side of the compressor via a suction pipe2047 which penetrates the side wall of a sealed case made of iron.

A body frame 2005 made of cast iron secures a fixed scroll 2015 and iswelded to the side wall of the sealed case at several points.

A drive shaft 2004 connected to the motor 3 is supported by a mainbearing 2012 disposed adjacent to the compression portion of the bodyframe 2005 and an upper bearing 2011 adjacent to the motor, and itscrank shaft 2014 is slidably connected to the portion including a rotarybearing 2018b of a rotary scroll 2018.

The discharge chamber oil reservoir 2034 is allowed to communicate withan oil chamber 2078a of the main bearing 2012 adjacent to thecompression chamber via an oil suction path 2038 formed in the bodyframe 2005 and the fixed scroll 2015.

An oil chamber 2078b formed by the crank shaft 2014 and the rotarybearing 2018b is allowed to communicate with a back pressure chamber2039 via a small hole 2040 formed in a rotary boss portion 2018e of therotary scroll 2018 and as well as allowed to communicate with the oilchamber 2078a via a gap of the sliding portion of the rotary bearing2018b.

It is arranged in such a manner that an outer space 2037 of the rotaryscroll 2018 and the back pressure chamber 2039 are intermittentlyallowed to communicate with each other via a key seat 2071 of the rotaryscroll 2018, which is arranged to be engaged with an Oldham's ring 2024and the oil groove 291 formed in the thrust bearing 220 only when thesecond compression chambers 51a and 51b (see FIG. 17) are allowed tocommunicate with the suction chamber 17. The second compression chambers51a and 51b (see FIG. 17) are allowed to communicate with the suctionchamber 17.

Each of the oil grooves 291 and the key seats 2071 formed in two placesare positioned to confront each other so as to be intermittently allowedto communicate with each other by making a phase angle between the backpressure chamber 2039 and the outer space 2037 when the rotary scroll2018 performs the rotary motion.

Since the other structures are the same as those according to the firstand second embodiments, their descriptions are omitted here.

Then, the operation of the scroll compressor thus-constituted will nowbe described.

Referring to FIGS. 4 to 19, when the drive shaft 4 is rotated by themotor 3, the rotation of the rotary scroll 18 around the main axis ofthe drive shaft 4 by means of the crank mechanism of the drive shaft 4is prevented because the key portion (see FIG. 5) of the Oldham's ring24 adjacent to the rotary scroll 18 is engaged with the key seal 71 ofthe rotary scroll and the key portion disposed in the opposing portionis engaged with the key groove 71a of the body frame 5. Therefore, itperforms a rolling motion so that it changes the capacity of thecompression chamber in association with the fixed scroll 15. As aresult, the suction and the compression operations of the refrigerantgas are performed.

The refrigerant in the form of a mixture of gas and liquid containingthe lubricating oil sucked from a refrigerating cycle connected to thecompressor is introduced into the accumulator chamber 46 through thesuction pipe 47 before it conflicts the outer surface of the end plate15b of the fixed scroll 15. Then, it passes through a space above theaccumulator chamber 46 before it is introduced into the suction chamberthrough the two suction holes 43.

On the other hand, the liquid refrigerant and the lubricating oilseparated from the refrigerant gas due to the difference in the weightbetween the gas and liquid and the inertia force at the time of changingin the direction of the flow are temporarily gathered in the bottomportion of the accumulator chamber 46. Then, they are, in the form ofmist, upward sucked into the suction hole 43 via the oil suction hole 9aand the oil suction hole 9b due to the negative pressure generated whenthe sucked refrigerant gas passes through the suction hole 43 beforethey are again mixed to the sucked refrigerant gas.

The sucked refrigerant gas is, after the gas and the liquid have beenseparated from each other, enclosed in the compression chamber after ithas passed through the suction chamber 17 and the first compressionchambers 61a and 61b formed between the rotary scroll 18 and the fixedscroll 15. Then, it is sequentially conveyed, while being compressed, tothe second compression chambers 51a and 51b and the third compressionchambers 60a and 60b before it is discharged to the check valve chamber50a through the discharge port 16 formed at the central portion. Then,it is discharged to the motor chamber 6 after it has sequentially passedthrough the discharge chamber 2, the gas path 80b, the gas path 80a andthe discharge chamber 2b.

Since the compression chamber and the discharge port 16 are allowed tocommunicate with each other after the compression has been completed,the compressed refrigerant gas is rapidly primary-expanded when it isintroduced from the compression chamber into the check valve chamber50a. During the discharge completion stroke immediately after this tothe compression completion stroke, the discharged refrigerant gas fromthe check valve chamber 50a primarily reversely flows into thecompression chamber.

As a result, the refrigerant gas is, on the whole, discharged from thecompression chamber into the discharge chamber 2 while repeating theintermittent discharge and introduction to and from the compressionchamber. The refrigerant gas discharged from the check valve chamber 50aand the discharge chamber 2 encounters a pulsation phenomenon becausethe pressure is changed when it is introduced/discharged to and from thecompression chamber.

The pulsation of the discharged refrigerant gas is sequentially reduceddue to the secondary expansion taken place when the refrigerant gas isintroduced into the discharge chamber 2 via the discharge apertures 50hof the check valve device 50 and the third and fourth expansions takenplace when the same is introduced from the two discharge paths 80 intothe discharge chamber 2b and the motor chamber 6. As a result, thepressure change in the motor chamber 6 can be substantially damped.

When the discharge refrigerant gas instantaneously reversely flows fromthe discharge chamber 2 to the check valve chamber 50a, the valve body50b tends, while following the above-described flow, to move in adirection in which it closes the discharge port 16. However, since thecoil spring 50c having the shape memory characteristic depending uponthe atmospheric temperature is completely contracted and thereby it doesnot give the urging force the valve body 50b during the operation of thecompressor and as well as the magnetized valve body 50 adheres to thebottom surface of the check valve chamber 50 and thereby it does notseparate from the same, the valve body 50b does not cover the dischargeport 16.

The discharged refrigerant gas scattered and discharged from theapertures 81a of the discharge guide 81 into the motor chamber 6 comesin contact with the annular shielding plate 86 and the wound wire of themotor 3 before it passes through the paths on the inside and outside thestator 3b toward the upper side portion of the motor chamber 6 whilecooling the motor 3. Then, it passes into the external refrigeratingcycle through the discharge pipe 31.

At this time, the lubricating oil contained in the dischargedrefrigerant gas is partially separated from the refrigerant gas becauseit adheres to the surface of the wound wire positioned in the lowerportion of the motor 3, the separated lubricating oil being gatheredinto the discharge chamber oil reservoir 34. However, the lubricatingoil in the discharged refrigerant gas, which passes through the outerportion of the upper balance weight 75 and the lower balance weight 75,is centrifugal-separated by the rotation of the upper balance weight 75and the lower balance weight 76 before it is dispersed on the innersurface of the wound wire of the motor 3. It then moves downward alongthe internal space of the wound wire bundle before it is gathered in thedischarge chamber oil reservoir 34.

The release gap 27 on the back side of the thrust bearing 20 which isallowed to communicate with the compression chamber (the compressionspace at the stroke immediately before the portion at which thecompression chamber communicates with the discharge port 16) in thefinal compression stroke is filled with the high pressure refrigerantgas immediately after the compression has been commenced. The thrustbearing 20 is pushed against the end plate fastening surface 15b1 of thefixed scroll 15 by the urging force of its back pressure and the elasticforce of the seal ring 70. As a result, the wrap support disc 18c of therotary scroll 18 is held between the end plate sliding surface 15b2 andthe thrust bearing 20.

The lubricating oil in the discharge chamber oil reservoir 34 isintroduced into the back pressure chamber 39 after the passage to bedescribed later so as to gradually raise the pressure of the backpressure chamber, the back pressure pushing the wrap support disc 18c ofthe rotary scroll 18 against the end plate sliding surface 15b2. As aresult, the gap present between the front portion of the fixed scrollwrap 15a and the wrap support disc 18c of the rotary scroll 18 iseliminated. Therefore, the compression chamber is sealed so that thesucked refrigerant gas is efficiently compressed and thereby the safetyoperation is continued.

The axial directional gap between the front portion of the rotary scrollwrap 18a and the fixed scroll 15 is sealed because the refrigerant gasis introduced into the tip seal groove 98 when the refrigerant gas leaksinto the adjacent low pressure compression chamber during thecompression and the gas back pressure generated in the tip seal groove98 pushes the tip seal 98a against the side surface of the bottomcompression chamber of the tip seal groove 98a and the fixed scroll 15.

After the operation of the compressor has been stopped, the rotaryscroll 18 instantaneously performs the reverse rotation due to thereverse flow due to the pressure difference of the refrigerant gas inthe compression chamber. However, the rotary scroll 18 is stopped at therotary angle in a state as shown in FIG. 17 in which the firstcompression chambers 61a and 61b are allowed to communicate with thesuction chamber 17 because the refrigerant gas reversely flows from thecompression chamber to the suction chamber 17. As shown in FIG. 11, theannular ring 94 closes the lubricating oil introduction port into theback pressure chamber 39.

After the operation of the compressor has been stopped, the refrigerantgas in the compression chamber reversely flows into the suction chamber17, causing the pressure of the refrigerant gas at the discharge port 16to be rapidly lowered. As a result, the generated pressure differencebetween the discharge port 16 and the discharge chamber 2 causes thevalve body 50b to close the discharge port 16. Therefore, the continuousreverse flow of the discharged refrigerant gas from the dischargechamber 2 into the compression chamber is prevented.

The magnetized valve body 50b is separated from the bottom surface ofthe check valve chamber 50a due to the pressure difference after theoperation of the compressor has been stopped to the pressure balance inrefrigerating cycle is established. As a result, the valve body 51bcontinues to close the discharge port 16. Simultaneously, the coilspring 50 possessing the shape memory characteristic is elongated due tolowering of the temperature. As a result, the valve body 50b continuesto close the discharge port 16 due to the urging force of the coilspring 50.

The first compression chambers 61a and 61b, which are intermittentlyallowed to communicate with the suction chamber 17, and the backpressure chamber 39 are allowed to communicate with each other via theoil hole 91 formed in the thrust bearing 20 only when the firstcompression chambers 61a and 61b are allowed to communicate with thesuction chamber 17. Furthermore, the reverse flow of the refrigerant gasinto the back pressure chamber 39 from the compression chamber duringthe compression is prevented because the portion between the thrustbearing 20 and the wrap support disc 18c are sealed by the lubricatingoil film.

During the stoppage of the operation of the compressor, the pressure isbalanced in the compressor and thereby the liquid refrigerant isintroduced into the compression chamber as well as the accumulatorchamber 46. Therefore, the liquid compression can easily take place atthe initial stage of the cool start of the compressor. Therefore, thrustforce in a direction opposing the discharge port 16 acts on the rotaryscroll 18 due to the pressure of the compressed refrigerant in thecompressor.

On the other hand, the pressure in the back pressure chamber 39 is lowat the initial stage of the cool start of the compressor. Therefore, thewrap support disc 18c of the rotary scroll 18 is separated from the endplate sliding surface 15b2 until it reaches the thrust bearing 20 atwhich it is supported at this retraction position. As a result, a gap isgenerated between the wrap support disc 18c and the front portion of thefixed scroll wrap 15a, causing the pressure in the compression chamberto be reduced. Therefore, the compression load at the initial stage ofthe start is reduced.

If the pressure in the compression chamber is instantaneouslyexcessively raised due to, for example, the liquid compression takenplace in the compression chamber, the thrust force acting on the rotaryscroll 18 is enlarged than the urging force caused by the back pressureacting on the back side of the rotary scroll 18. As a result, the rotaryscroll 18 is moved in the axial direction so as to be supported by thethrust bearing 20. Then, the sealing of the compression chamber is,similarly to the above-described case, cancelled and thereby thepressure in the compression chamber is lowered, causing the compressionload to be reduced.

The lubricating oil in the discharge chamber oil reservoir 34 at theinitial stage of the cool start of the compressor is sucked into the oilchamber 78a via the oil hole 38a by the screw-pump operation of thespiral oil grooves 41a and 41b formed in the drive shaft 4.

Then, a portion of the lubricating oil lubricates the sliding surface ofthe rotary bearing 18bafter it has passed through the spiral oil groove41b, the oil chamber 78b and the oil supply hole 73a before it issupplied to the sliding surface of the main bearing 12, the portion ofthe lubricating oil being then supplied to the oil reservoir 72.

The lubricating oil supplied to the main bearing 12 by means of thespiral oil groove 41a joins the lubricating oil, which has passedthrough the oil chamber 78b, at the oil reservoir 72. Then, the pressureof a portion of the lubricating oil is reduced at the throttle pathportion of the oil hole 38b before it is intermittently supplied to theback pressure chamber 39. The residual portion of the lubricating oillubricates the sliding surface of each of the upper bearing 11 and thethrust bearing 13 before it is recovered again in the discharge chamberoil reservoir 34.

The oil reservoir 72 and the motor chamber 6 are cut off from each otherby the sealing action performed by the oil film which lubricates theupper bearing 11.

The pressure in the motor chamber 6 is raised after the lapse of timefrom the initial stage of the cool start of the compressor and therebythe lubricating oil in the discharge chamber oil reservoir 34 is suckedinto the oil chamber 78a due to also the pressure difference from theback pressure chamber 39. Then, it is supplied to the back pressurechamber 39 as well as by virtue of the screw-pump action performed bythe spiral oil grooves 41a and 41b, causing the pressure in the backpressure chamber 39 to be successively raised.

Since the annular ring 94 rotates together with the rotary scroll 18 inthe configuration in which the center of the compression chamber, thecenter of the rotary bearing 18e and the center of the annular ring 94are made to coincide with each other. Therefore, the annular ring 94tends to jump the annular seal groove 95 formed in the rotary bossportion 18e due to the inertia force at the time of the rotary motion.As a result, the annular ring 94 is pushed against the body frame 5 andthe outer surface of the annular seal groove 95. Furthermore, thelubricating oil is pushed into the portion between the annular sealgroove 95 and the annular ring 94 due to the oil scraping actionperformed by the annular ring 94. As a result, the annular ring 94 ispushed also due to the generation of the dynamic pressure at this timeso that the portion between the oil chamber 78a and the back pressurechamber 39 are sealed.

Furthermore, the annular ring 94 is pushed to the outer surface of theannular seal groove 95 also due to the pressure difference between theback pressure chamber 39 and the oil chamber 78a. Therefore, theabove-described two spaces can be further assuredly sealed.

The sliding surface between the annular ring 94 and the body frame 5 issealed by the oil film of the lubricating oil retained in the oil groove94a formed in the surface of the annular groove 94 and as well as thewear and the resistance due to the sliding taken at the sliding surfaceare reduced.

The rotary scroll 18 is equally urged with the back pressure toward thefixed scroll 15 by the pressure of the lubricating oil in the highpressure oil chamber 78a and the pressure of the lubricating oil in theintermediate pressure back pressure chamber 39. As a result, the wrapsupport disc 18c and the end plate sliding surface 15b2 smoothly slideeach other and as well as the deformation of the wrap support disc 18cis reduced, causing the axial directional gap of the compression chamberto be minimized.

The lubricating oil introduced into the back pressure chamber 39 isintermittently introduced into the outer space 37 via the oil hole 91formed in the thrust bearing 20. Furthermore, the pressure of it isgradually reduced when it passes through the oil hole 38c formed in thewrap support disc 18c and the injection hole 52 having a small diameterbefore it is introduced into the second compression chambers 51a and 51bwhile lubricating each sliding surface through the path to seal the gapin the sliding portions.

The lubricating oil introduced into the second compression chambers 51aand 51b joins the lubricating oil introduced into the compressionchamber together with the sucked refrigerant gas to seal the small gapin the adjacent compression chambers with the oil film. As a result, itprevents the leakage of the compressed refrigerant gas and is againdischarged into the motor chamber 6 together with the compressedrefrigerant gas while lubricating the sliding surface betweencompression chambers.

In the oil supply path constituted from the discharge chamber oilreservoir 34 to the second compression chambers 51a and 51b via the backpressure chamber 39, a proper intermediate pressure level between thedischarge pressure and the sucked pressure is maintained in the backpressure chamber 39. The pressure of each of the opening portions of theinjection holes 52a and 52b of the second compression chambers 51a and51b changes as shown in FIG. 19. Therefore, it is instantaneously higherthan the back pressure chamber pressure 68 which is changed followingthe pressure of the motor chamber 6. However, the back pressure chamber39 and the outer space 37 are arranged in such a manner that the wrapsupport disc 18c closes the opening end portion of the oil hole 91 ofthe thrust bearing 20 and the sliding surface between the wrap supportdisc 18c and the thrust bearing 20 is sealed with the oil film.Therefore, the refrigerant gas which is being compressed does notreversely flow into the back pressure chamber 39. Furthermore, theaverage pressure of the second compression chambers 51a and 51b is lowerthan that in the back pressure chamber 39.

As described above, the rotary scroll 18 at the initial stage at thecompressor start is separated from the fixed scroll 15 and is supportedby the thrust bearing 20 which receives the elastic force of the sealring 70 and the back pressure of the refrigerant gas introduced from thecompression chamber in the compression stroke.

The lubricating oil supplied to the back pressure chamber 39 due to thepressure difference after the start of the compressor has beenstabilized gives the rotary scroll 18 the urging force of theintermediate pressure. As a result, the wrap support disc 18c is pressedagainst the end plate 15b to seal the sliding surface with the oil filmso that the portion between the outer space 37 and the suction chamber17 is sealed.

The lubricating oil in the back pressure chamber 39 is present in thegap in the sliding surface between the thrust bearing 20 and the wrapsupport disc 18c so that the gap is sealed.

Since the compression ratio of the scroll compressor is constant, therotary scroll 18 separates from the fixed scroll 15 and is supported bythe thrust bearing 20 if the pressure of the sucked refrigerant gas isrelatively high as is shown in the case immediately after the cool startand thereby the pressure in the compression chamber is excessivelyraised or if an excessive liquid compression takes place.

However, since the thrust bearing 20 urged with the back pressure cannotbear the load due to the pressure of the compression chamber, which hasbeen excessively raised, it is retracted in a direction in which therelease gap 27 is reduced. As a result, the axial directional gapbetween the wrap support disc 18c of the rotary scroll 18 and the frontportion of the fixed scroll wrap 15a of the fixed scroll 15 is enlarged.As a result, a large quantity of leakage takes place in the portionbetween the compression chambers. Therefore, the pressure in thecompression chamber is rapidly lowered during the compression asdesignated by an alternate long and short dash line 63a of FIG. 18.

After the compression load has been instantaneously reduced, the thrustbearing 20 instantaneously restores its original position. Therefore,the pressure of the back pressure chamber 39 is not excessively lowered,causing the stable operation is again continued.

When the rotary scroll 18 retracts toward the thrust bearing 20, theaxial directional distance from the front portion of the rotary scrollwrap 18a to the fixed scroll 15 is lengthened. However, since the tipseal 98a is pressed toward the fixed scroll 15 by the gas pressure onits back side, the leakage of the compressed refrigerant gas from theabove-described portion can substantially be prevented.

If a foreign matter is caught in the axial directional gap between therotary scroll 18 and the fixed scroll 15, the thrust bearing 20 isretracted similarly to the above-described case, causing the foreignmatter to be removed.

The pressure in the compression chamber in a case where the liquidcompression is generated instantaneously at the time of the initialstage of the cool start or the normal operation takes place theexcessive compression as designated by a dashed line 63 of FIG. 18.However, the capacity of the high pressure space which is allowed tocommunicate with the discharge port 16 is large and expansions arerepeated during the sequential passage through the check valve chamber50a, the discharge chamber 2 and the discharge chamber 2b. Therefore,the pressure in the motor chamber 6 is not substantially changed.

Furthermore, the leakage of the refrigerant gas from the compressionchamber per unit time is reduced in proportion to the increase in theoperational speed of the compressor. On the contrary, the time in whichthe injection holes 52a and 52b per rotation is shortened, causing thequantity of oil injection into the compression chamber to be restricted.Furthermore, the passage resistance is increased due to the increase inthe cutting off speed between the oil hole 38b and the back pressurechamber 39. Therefore, the quantity of the lubricating oil to beintroduced from the oil chamber 78a into the back pressure chamber 39 isrestricted. As a result, the pressure in the back pressure chamber 39 isproperly retained.

The scroll refrigerant compressor which is included in the heat pumprefrigerating cycle and which is being operated is arranged in such amanner that the high pressure side is allowed to communicate with theevaporator and the low pressure side is allowed to communicate with thecondenser although its time is short when the heating operation isswitched to a moisture eliminating operation. Therefore, the pressure inthe motor chamber 6 is instantaneously lowered. Following it, thepressure in the back pressure chamber 39 allowed to communicate with themotor chamber 6 is lowered and thereby the proper back pressure will besometimes impossible to be retained. In this case, the plunger 29 of theback pressure control valve device 25 provided for the wrap support disc18c is moved toward the outer space 37 as shown in FIG. 16 against theback pressure force of the lubricating oil allowed to communicate withthe coil spring 53 and the back pressure chamber 39 by the pressure ofthe lubricating oil in the oil hole 54b allowed to communicate with theoil chamber 78b. As a result, the oil chamber 78b and the back pressurechamber 39 are allowed to communicate with each other so that the highpressure lubricating oil is introduced into the back pressure chamber39. As a result, the pressure of the back pressure chamber 39 isrestored to the proper pressure. Therefore, the plunger 29 is againmoved toward the oil chamber 78b as shown in FIG. 15, causing the oilchamber 78b and the back pressure chamber 39 to be cut off from eachother.

In a case where the thermal load on the evaporator side is large and thecondensing performance on the condenser side is large, the operation isperformed in such a manner that the suction pressure is relatively highand the discharge pressure is relatively low.

In this case, it is necessary for the pressure in the back pressure tobe raised in comparison to that at the normal state because the pressurein the compression chamber is higher than that at the normal operation.Also in this case similarly to the above-described case, the plunger 29is moved toward the outer space 37 as shown in FIG. 16 by the pressureof the lubricating oil in the oil hole 54b allowed to communicate withthe oil chamber 78b and the pressure of the refrigerant on the suctionside which is allowed to communicate with the suction chamber 17 via theoil hole 54a against the back pressure force of the lubricating oilallowed to communicate with the coil spring 53 and the back pressurechamber 39. As a result, the oil chamber 78b and the back pressurechamber 39 are intermittently (or partially) allowed to communicate witheach other, causing the high pressure lubricating oil to be introducedinto the back pressure chamber 39. As a result, the pressure of the backpressure chamber 39 is retained at the proper level.

The plunger 29 is, of course, influenced by the centrifugal force, theinertia force and frictional force acting on the plunger 29. Therefore,since it tends to be moved toward the outer space 37, the pressure inthe back pressure chamber 39 is raised following the increase in theoperational speed of the compressor.

Although the compressed refrigerant gas during the final compressionstroke is introduced into the release gap 27 formed on the back side ofthe thrust bearing 20 according to the above-described embodiment, thedischarged refrigerant gas in a region in which the compression chamberin the compression final stroke and the discharge port are allowed tocommunicate with each other may be introduced into the release gap 27.

According to the above-described embodiment, although the sliding gapbetween the wrap support disc 18c of the rotary scroll 18 and the thrustbearing 20 is sealed by only the oil film of the lubricating oil, anannular ring (82) shown in FIGS. 6 and 7 in Japanese Patent ApplicationNo. 63-159996 disclosed by the inventor of the present invention may befastened to the back side of the wrap support disc 18c. In this case,the performance of sealing the gap in the sliding portion between theback pressure chamber 39 and the outer space 37 can be further improved.

Then, the operation of the second embodiment will now be described withreference to FIGS. 20 to 24.

The pressure in the motor chamber 6 which is filled with the dischargedrefrigerant gas with the lapse of time after the compressor start.

The lubricating oil in the discharge oil reservoir 34 in the bottomportion of the motor chamber 6 is, similarly to the case shown in FIG.4, sucked into the oil chamber 278a via the oil hole 238a formed in thebody frame 205 by the screw-pump operations of the spiral oil grooves241a and 241b formed in the drive shaft 204. At this time, the partitioncap 101 guides the lubricating oil to make it flow in the portionadjacent to the surface of the drive shaft 204 to be introduced into theoil chamber 278a and the spiral oil groove 241b. As a result, thelubricating oil is not influenced by the centrifugal dispersion due tothe high speed rotation of the drive shaft 204 when it is introducedinto the oil chamber 278a from the oil hole 238a so that it is suckedinto the spiral oil groove 241a. As a result, a satisfactory screw-pumpoil supply can be performed.

The lubricating oil supplied to the oil chamber 278b by the pressuredifference between the discharge chamber oil reservoir 34 and the backpressure chamber 239 of the rotary scroll 218 and the screw-pump actionperformed by the spiral oil groove 241b lubricates the sliding surfaceof the rotary bearing 218b during it passes through the path. Then, itis introduced into the back pressure chamber 239 after it has passedthrough the throttle path 103, the annular groove 104 and the oil hole105.

The lubricating oil in the oil chamber 278a the pressure level of whichis substantially the same as that in the motor chamber 6 is lowered inpressure when it passes through the throttle path 103 and the oil hole105. As a result, the pressure in the back pressure chamber 239 isbrought to an intermediate level.

Similarly to the case shown in FIG. 4, the outer space 37 and the backpressure chamber 239 are allowed to communicate with each other via theoil groove 291 formed in the surface of the thrust bearing 220 only inthe rotary angular range in which the compression chamber is subjectedto the suction stroke. Therefore, the lubricating oil in the backpressure chamber 239 is intermittently supplied to the outer space 37.

The lubricating oil is then supplied to the compression chambersimilarly to the case shown in FIG. 4 before it is again discharged tothe motor chamber 6 together with the compressed refrigerant gas.

The lubricating oil supplied to the main bearing 212, the upper bearing211 and the thrust bearing 213 by the screw-pump action performed by thespiral oil groove 241a is again gathered in the discharge chamber oilreservoir 34.

Since the other operations are the same as those according to the caseshown in FIG. 4, their descriptions are omitted here.

Then, the operation of the third embodiment will now be described withreference to FIGS. 25 to 27.

Simultaneously with the compressor start, the lubricating oil in thedischarge oil reservoir 34 in the bottom portion of the motor chamber 6is sucked into the oil chamber 378a through the oil hole 338a formed inthe body frame 305 by the screw-pump action performed by the spiral oilgrooves 341a and 341b formed in the drive shaft 304 and by the trochoidpump device 106 disposed at the lower end portion of the drive shaft304. At this time, the partition cap 101 guides, similarly to the caseshown in FIG. 20, the lubricating oil to be introduced into the oilchamber 378a and the spiral oil groove 341b after it has passed throughthe portion adjacent to the surface of the drive shaft 304. Therefore,when the lubricating oil is introduced into the oil chamber 378a throughthe oil hole 338a, it is not influenced by the centrifugal dispersiondue to the high speed (for example, 6000 rpm or higher) of rotation ofthe drive shaft 304 so that it is smoothly sucked into the spiral oilgroove 341a. As a result, satisfactory screw-pump oil supply can beperformed.

The lubricating oil introduced into the suction hole 108 formed in thetrochoid pump device 106 after it has passed through the spiral oilgroove 341b while lubricating the sliding surface of the rotary bearing318bis discharged to the oil groove 111 before it is supplied to themain bearing 312 via the oil hole 112 and the radial directional oilhole 113. As a result, it is discharged to the oil reservoir 72. Thelubricating oil passing through the spiral oil groove 341a whilelubricating the main bearing 312 and discharged into the oil reservoir72 joins the lubricating oil discharged from the trochoid pump device106. A portion of the lubricating oil passes through the oil hole 38bwhile the pressure of which is reduced before it is intermittentlysupplied to the back pressure chamber 339.

The residual portion of the lubricating oil discharged into the oilreservoir 72 lubricates the upper bearing 311 and the thrust bearingportion 313 before it is gathered in the discharge chamber oil reservoir34.

The pressure in the motor chamber 6 which is filled with the dischargedrefrigerant gas with the lapse of time after the compressor start isgradually raised. Therefore, the lubricating oil in the dischargechamber oil reservoir 34 is supplied to the back pressure chamber 339also due to the pressure difference between the discharge chamber oilreservoir 34 and the back pressure chamber 339 of the rotary scroll 318.

Since the oil supply operation from the back pressure chamber 339 to thecompression chamber and the other operations are the same as thoseaccording to the case shown in FIG. 20, their descriptions are omittedhere.

Then, the operation of the fourth embodiment will now be described withreference to FIGS. 28 to 30.

Simultaneously with the compressor start, the crank shaft 414 performsthe eccentric rotation by the rotation of the drive shaft 404. Therotary scroll 418 does not rotate on its own axis but it revolves aroundthe main axis of the drive shaft 404 by the rotation prohibitingmechanism of the Oldham's ring 24 which is permitted to perform only thereciprocating motion.

While following the rotational motion performed by the rotary bearing418b fixed to the rotary scroll 418, the piston 115 which engages withit performs the rotary motion. As a result, the front portion of thepartition vane 117 is urged by the coil spring 116, causing a known oilsupply pump which slidably comes in contact with the piston 115 performthe suction and discharge operations.

The lubricating oil in the discharge chamber oil reservoir 34 isintroduced into the suction cut portion 114 via the oil hole 438a formedin the body frame 405 before it passes through the pump chamber and isdischarged into the groove 119 of the side plate case 118. Then, it issupplied to the oil chamber 478b and the axial directional oil hole 112aformed in the drive shaft 404 from the oil chamber 478a also by thescrew-pump action (the viscous pump action) performed by the spiral oilgroove 441b while lubricating the sliding surface of the rotary bearing414 so that it lubricates the sliding surface of the main bearing 412.

The lubricating oil sucked into the spiral oil groove 441a by therolling piston type oil supply pump is supplied to the main bearing 412by the screw-pump action before it joins the lubricating oil dischargedfrom the axis directional oil hole 112. As a result, similarly to thecase shown in FIG. 25, it is discharged to an oil reservoir 72 (omittedfrom illustration), the upper bearing and the thrust bearing portion andas well as supplied to the back pressure chamber 439 via the oil hole438a while the pressure of which is being reduced. As a result, eachsliding portion at the initial stage of the compressor start islubricated.

The end portions of the opening side of the oil hole 438b of the backpressure chamber 439 is intermittently opened/closed by thereciprocating motion performed by the Oldham's ring 24. The continuouslyopened time is shortened in inverse proportion to the rotational speedof the drive shaft 404. Therefore, the introduction resistance into theback pressure chamber 439 is increased. As a result, the quantity of thelubricating oil to be introduced into the back pressure chamber 439 isdecreased.

With the lapse of time after the compressor stat, the pressure of thedischarged refrigerant gas acting on the discharge chamber oil reservoir34 is raised. Then, the lubricating oil in the discharge chamber oilreservoir 34 is supplied to the oil chamber 478a also due to thepressure difference from the back pressure chamber 439. Then, it issupplied to each sliding portion by the screw-pump actions of the spiraloil grooves 441a and 441b.

By the oil supply means constituted by employing the above-describedpressure-difference oil supply, the capacity type oil supply pump (therolling piston type oil supply pump device) and the viscous pump (screwpump), satisfactory oil supply to the sliding portion can be continuedeven if a certain quantity of gas engagement takes place in thelubricating oil or if the oil supply performance of the capacity typeoil supply pump or the viscous pump is deteriorated in the high speedoperational region.

Since the other operations are the same as those according to the casesshown in FIGS. 4, 20 and 25, their descriptions are omitted here.

Then, the operation of the fifth embodiment will now be described withreference to FIGS. 31 to 33.

The piston 115 having the projecting portion 115b movably fitted to thecut groove 121 of the body frame 505 performs the swing motion when therotary bearing 518b of the rotary scroll 518 performs the rotary motionso that the suction and discharge operations are performed. Since thegap is formed between the inner surface of the piston 115a and thesmall-diameter outer portion 518f of the rotary bearing 515b, thequantity of movement of the piston 115 is smaller than a value which istwo times the quantity of eccentricity of the crank shaft 514. The sizeof the gap determines the discharge quantity possessed by the rotarycylindrical piston type oil supply pump. According to this embodiment,the quantity of movement of the piston 115a is established to a valuecorresponding to the quantity of eccentricity of the crank shaft 514 soas to restrict the input and to secure the oil supply quantity at thetime of the high speed operation.

Simultaneously with the compressor start, the lubricating oil in thedischarge chamber oil reservoir 34 is sucked into the suction hole 114cformed in the side plate 114b via the oil hole 538a before it isdischarged through the groove 115c of the piston 115a and is thensupplied to the oil chamber 578a.

The lubricating oil in the oil chamber 578a is supplied to the rotarybearing 518b and the main bearing 512 by the screw-pump action performedby the spiral oil groove 541b so that it is used to lubricate eachsliding surface.

Since the ensuing operations are the same as those according to theabove-described embodiments, their descriptions are omitted here.

Then, the operation of the sixth embodiment will now be described withreference to FIGS. 34 and 35.

Simultaneously with the compressor start, the rotor fixed to the driveshaft 604 is rotated, causing the vane 123 slidably fastened to therotor 122 to be moved to the outer portion of the rotor 123 due to itscentrifugal force. As a result, the pump chamber is sectioned so thatknown suction and discharge operations are performed.

The lubricating oil in the discharge oil reservoir 34 is sucked throughthe suction hole 118c of the side plate case 118bvia the oil hole 638abefore it is discharged into the oil chamber 678a via the discharge hole125.

In a case where the pressure in the pump chamber is raised to exceed thepredetermined pressure due to the high speed rotation of the drive shaft604, the force of the lubricating oil acting on the front portion of thevane 123 from the pump chamber portion is made to be larger than thecentrifugal force of the vane 123. As a result, the vane 123 isretracted, causing the gap between the pump chambers to be widened. As aresult, the oil supply performance of the pump is controlled.

At the time of the extremely low speed operation, the centrifugal forceof the vane 123 is small. Therefore, the sections in the pump chambercannot be sufficiently formed, causing the oil supply performance of thepump to be restricted. As a result, the liquid refrigerant retained Inthe bottom portion of the discharge chamber oil reservoir 34 is notsupplied to the bearing sliding portion at the initial stage at the coolstart of the compressor.

With the lapse of time after the start of the compressor, the liquidrefrigerant retained in the discharge oil reservoir 34 is separated fromthe lubricating oil while foaming so that it is moved to the upperportion of the motor chamber 6. Then, the oil supply pumping effect issufficiently exhibited in the normal operational speed region of thecompressor. As a result, the lubricating oil containing no refrigerantis supplied to each sliding portion.

Since the other operations are the same as those according to the caseshown in FIG. 31, their descriptions are omitted here.

Then, the operation of the seventh embodiment will now be described withreference to FIG. 36.

The sucked refrigerant gas is introduced into the accumulator chamber746 through the suction pipe 47 due to the rotation of the drive shaft704. Then, the discharged refrigerant gas is, after it has been suckedand compressed, introduced into the oil separation chamber 128 via thedischarge chamber 2, the gas path 780b, the gas path 780a and thedischarge bypass pipe 127.

The discharged refrigerant gas introduced into the oil separationchamber 128 conflicts the upper frame 126 at which a portion of thelubricating oil is separated. Then, it cools the motor 703 via the gashole 129 and the upper space of the motor chamber 706 while separating aportion of the lubricating oil. Then, it is discharged through thedischarge pipe 731 disposed outside the lower motor coil end 130.

The lubricating oil separated from the discharged refrigerant gas in theoil separation chamber 128 lubricates the sliding surface of the bearingafter it has passed through the spiral oil groove 741d formed in the topend shaft 704d of the drive shaft 704. Then, it is introduced into themotor chamber 706 before it is gathered in the discharge chamber oilreservoir 734 formed in its lower portion.

With the lapse of time after the start of the compressor, the pressurein the motor chamber 706 is raised. In accordance with this, thelubricating oil in the discharge chamber oil reservoir 34 is sucked intothe oil chamber 778a via the oil hole 738a formed in the body frame 705by the pressure difference from the back pressure chamber 739 and thescrew-pumping action performed by the spiral oil grooves 741a and 741bformed in the drive shaft 704. Then, it is supplied to the main bearing712 and the oil chamber 778b.

The lubricating oil in the oil chamber 778b is supplied to the mainbearing 712 due to the centrifugal pumping oil supply action suppliedvia the axial directional oil hole 112. Then, it joins the lubricatingoil which has passed through the spiral oil groove 741a before it isdischarged into the oil reservoir 772.

The lubricating oil further lubricates the thrust bearing portion 713before it is gathered in the discharge chamber oil reservoir 734 and thesame is as well as reduced in its pressure at the throttle path portionin the oil hole 738b so as to be intermittently supplied to the backpressure chamber 739.

Since the portion between the oil reservoir 772 and the motor chamber706 is gas-sealed by the film of the lubricating oil supplied to thethrust bearing portion 713, the refrigerant gas in the motor chamber 706is not directly introduced into the back pressure chamber 739.

The release gap (see FIG. 13) on the back side of the thrust bearing 20allowed to communicate with the compression chamber of the finalcompression stroke is communicated via the throttle path between thescrew portion gap of the bolt 710 positioned at an intermediate positionin the communication path. Therefore, the compressed refrigerant gas atthe initial stage of the start of the compressor is introduced into therelease gap while the pressure of which is reduced. As a result,although the gas pressure at the release gap is low immediately afterthe start of the compressor, it is raised with the lapse of time afterthe start of the compressor so that the thrust bearing 20 abuts againstthe fixed scroll 715 by the force of the gas back pressure.

The axial directional movement of the rotor 703a disposed between thethrust bearing portion 713 of the body frame 705 and the upper frame 126is restricted by selecting the axial directional dimensions of the upperbalance weight 775 and the lower balance weight 776.

The lower balance weight 776 slides on and comes in contact with thethrust bearing portion 776 so as to bear the weight of the drive shaft704 and that of the rotor 703a.

The axial directional movements of the drive shaft 704 and the rotor703a are generated at the time of the jumping phenomenon generated dueto the incomplete flatness of the sliding surface when the lower balanceweight 776 slides and comes in contact with the thrust bearing 713 athigh speed. However, since the axial directional movement is restricted,the degree of the above-described movement can be reducedsatisfactorily.

Since the other operations are the same as those according to the caseshown in FIG. 4, their descriptions are omitted here.

Then, the operation of the eighth embodiment will now be described withreference to FIG. 37.

The refrigerant gas sucked through the suction pipe 47 is dischargedinto the outer refrigerating cycle through the upper discharge pipe 831via the check valve chamber 50a, the discharge chamber 2, the gas path880b, the gas path 880b, the discharge chamber 2b, the motor chamber806, the gas hole 229 and the oil separation chamber 128a while coolingthe motor 703 after it has been compressed in the compression chamber.The lubricating oil contained in the discharged refrigerant gas isprimarily separated in the motor chamber 806 and is secondarilyseparated in the oil separation chamber 128a before the lubricating oilis gathered in the bottom portion at the central portion of the upperframe 126 which supports the top end portion of the drive shaft 704.Then, it lubricates the sliding surface of the bearing before it isreturned to the motor chamber 706.

The oil supply to the main bearing 812 of the body frame 805, the thrustbearing portion, the back pressure chamber 839, the rotary bearing andthe like are performed similarly to the case shown in FIG. 36.

Since the back side of the thrust bearing 220 is allowed to directlycommunicate with the discharge chamber oil reservoir 34 and the urgingforce for pressing the thrust bearing 220 against the fixed scroll 815depends upon the pressure of the lubricating oil in the dischargechamber oil reservoir 34 and the elastic force of the coil spring 131and the seal ring 70a, the force for supporting the thrust bearing 220is small at the time of the initial stage of the cool start of thecompressor at which the pressure in the motor chamber 806 is low.Therefore, the thrust bearing 220 cannot bear the load when the rotaryscroll 818 is retracted toward the thrust bearing 220 due to thepressure in the compression chamber at the time of the start of thecompressor. As a result, it is retracted in a direction in which therelease gap is narrowed, causing the axial directional gap of thecompression chamber to be enlarged. Therefore, the pressure in thecompression chamber is rapidly lowered, causing the compression load atthe time of the initial stage of the start of the operation is reduced.

A small gap is formed between the body frame 805 and the outer surfaceof the thrust bearing 220 so that the thrust bearing 220 is able to movein the axial direction. Therefore, the lubricating oil in the dischargechamber oil reservoir 34 is introduced into the above-described gap.

The above-described lubricating oil is subjected to the liquidcompression process performed in the compression chamber so that therotary scroll 818 is retracted toward the thrust bearing 220 and alsothe thrust bearing 220 is retracted. Therefore, it is introduced intothe outer space 37 when the gap is formed between the thrust bearing 220and the fixed scroll 815. As a result, the pressure of the back pressurechamber 839, which is allowed to communicate with the outer space 37, isquickly raised, causing the rotary scroll 818 to be pressed and therebyreturned to the position toward the fixed scroll 815.

The liquid compression at the initial stage of the start of thecompressor can be reduced or prevented by switching the electric supplycircuit to the motor 703, the speed of which is varied by a DC powersource, immediately before the start of the compressor in a state wherethe check valve device closes the discharge port to reversely rotate themotor 703 by two to three times at extremely low speed and to dischargethe liquid refrigerant and the lubricating oil in the compressionchamber into the accumulator chamber 846 and by forward rotating themotor 703.

Since the other operations are the same as those according to the casesshown in FIGS. 4 and 36, their descriptions are omitted here.

Then, the operation of the ninth embodiment will now be described withreference to FIG. 38.

The lubricating oil in the discharge chamber oil reservoir 34 which hasbeen introduced into the back pressure chamber 939 after it has passedthrough the bearing sliding portion for supporting the drive shaft 4 andthe bearing joint portion between the rotary scroll 918 and the driveshaft 4 urges the rotary scroll 918 against the fixed scroll 915 withits back pressure. Furthermore, the pressure of it is reduced and isintroduced into the outer space 37 via the oil groove 291 formed in thethrust bearing 220 in a period in which the second compression chambers51a and 51b are allowed to communicate with the suction chamber 17.

The lubricating oil introduced into the outer space 37 lubricates thesliding surface between the lap support disc 918c of the rotary scroll918 and the thrust bearing 220 and the sliding surface between the lapsupport disc 918c and the end plate sliding surface 915b2 of the fixedscroll 915 before it is introduced into the oil hole 938c and theinjection hole 952 in a period in which the second compression chambers51a and 51b are allowed to communicate with the suction chamber 17 atwhich it is reduced in pressure. Then, it is introduced into thecompression chamber so that the gap of the compression chamber is sealedby its oil film and it is mixed with the compressed gas before it isagain discharged into the discharge chamber 2.

In a case where the pressure in the compression chamber isinstantaneously abnormally raised due to the liquid compressionoperation performed in the compression chamber or the like, thecompressed gas tend to reversely flow into the outer space together withthe lubricating oil present in the path. However, its pressure level islowered due to the influence of the viscous resistance of thelubricating oil retained in the oil reservoir path 938e or the passageresistance of the throttle path 938d. Furthermore, since the lap supportdisc 918c closes the end portion of the oil hole 938c, the reverse flowof it into the outer space 37 is prevented.

During the above-described compression stroke, the lap support disc 918ccuts off the portion between the outer space 37 and the back pressurechamber 939.

Since the other operations are the same as those according to the firstand second embodiments, their descriptions are omitted here.

Then, the operation of the tenth embodiment will now be described withreference to FIG. 39.

The lubricating oil in the discharge chamber oil reservoir 2034 isintroduced into the compression chamber via the following pressuredifference path due to the pressure difference between the dischargechamber oil reservoir 2034, on which the discharge pressure acts, andthe compression chamber. While it passes through the path, it is used tolubricate the sliding portion, give the back pressure to about therotary scroll 2018 toward the fixed scroll 2015 and to seal with the oilfilm for the purpose of preventing the gas leakage from the gap betweenthe sliding portions.

That is, the lubricating oil in the discharge chamber oil reservoir 2034is introduced into the oil chamber 2078a via the oil suction path 2038formed between the body frame 2005 and the fixed scroll 2015.

The lubricating oil in the oil chamber 2078a is supplied to the mainbearing 2012 and the upper bearing 2011 by the spiral oil groove formedin the drive shaft 2004. Furthermore, it is secondarily reduced inpressure via the gap in the bearing between the crank shaft 2014 and therotary bearing 2018bbefore it is introduced into the oil chamber 2078b.Then, it is secondarily reduced in pressure via the thin hole 2014before it is introduced into the back pressure chamber 2039.

The opening portions of the two thin holes 2040 formed in the rotaryboss portion 2018e facing the back pressure chamber 2039 are positionedadjacent to the key seat 2071a in the fastening and sliding portionbetween Oldham's ring 2024 and the body frame 2005. Therefore, thelubricating oil introduced from the oil chamber 2078b into the backpressure chamber 2039 is forcibly used to lubricate the sliding surfaceof the key groove 2071a.

The lubricating oil in the back pressure chamber 2039 passes through thetwo key grooves 2071 formed in the rotary scroll 2018 and the twoshallow grooves 291 formed in the thrust bearing 220 before it makes aphase angle of 180° while lubricating the sliding surface of the keygroove 2071. Then, it is intermittently introduced into the outer space2037 from the opposite positions after they have been third reduced inpressure.

The path through which the lubricating oil is introduced from the outerspace 2037 into the compression chamber is the same as that according tothe first and second embodiments.

The drive shaft 2004 comes in contact with the end surface of the rotaryboss portion 2018e of the rotary scroll 2018 by the pressure differencebetween the oil chamber 2078a and the oil chamber 2078b so as to beslidably supported.

The top end portion of the spiral oil groove formed in the drive shaft2004 is not opened at the top end portion of the upper bearing 2011 andthe bearing gap of the upper bearing 2011 is sealed by the film of thelubricating oil present in the bearing gap of the upper bearing 2011.Therefore, the discharged refrigerant gas is not introduced into thebearing and the back pressure chamber 2039.

The surface at which the fixed scroll 2015 and the body frame 2005 arecoupled to each other is surrounded by the lubricating oil from thedischarge chamber oil reservoir 2034. Therefore, the introduction of thehigh pressure refrigerant gas into the outer space 2037 via theabove-described surface is prevented by the oil film enclosed in theabove-described surface. Therefore, the introduction of the highpressure refrigerant gas into the outer space 2037 can be prevented.

The refrigerant gas introduced into the suction chamber 17 via thesuction pipe 2047 is discharged into the discharge chamber 2 after ithas been compressed. Then, it is discharged into the discharge chamber2002b via the two discharge paths 2080 disposed symmetrically before itis supplied to the outer refrigerating cycle through the discharge pipe2031 via the motor chamber 2006.

The pressure pulsation and the discharge noise of the dischargerefrigerant as to be discharged into the discharge chamber 2002b fromthe discharge paths 2080 disposed symmetrically are interfered with eachother and thereby damped. Then, the pressure pulsation is reduced whenit is again equally discharged from the discharge chamber 2002b into themotor chamber 2006. As a result, the pressure pulsation of the motorchamber 2006 allowed to communicate with the external pipe system can bedamped to a degree which does not influence the vibration of theexternal pipe system.

The discharge noise generated when the compressed refrigerant gas isdischarged from the compression chamber to the discharge chamber 2 isshielded by the lubricating oil in the discharge chamber oil reservoir2034 surrounding the compression chamber and the discharge chamber 2.Therefore, it is not transmitted to outside the sealed case 2001.

The discharge noise generated when the compressed refrigerant gas isdischarged from the compression chamber to the discharge chamber 2 israised in level in proportion to the operational speed of thecompressor. In a case where the operational speed of the compressor isin the normal operational region (for example, 5000 rpm or lower), thedischarge chamber 2002b may be eliminated and the discharged refrigerantgas may be directly discharged to the motor chamber 2006 through the twodischarge paths 2080 extended (for example, a discharge path ordischarge pipe is provided). In this case, the more the distance betweenthe positions of the openings of the two discharged paths extended anddisposed symmetrically, the discharge noise and the pressure pulsationcan be damped satisfactorily.

Although the first to the tenth embodiments are described, a propercombination of the above-described embodiment may be employed to meetthe operational conditions of the compressor.

(1) As described above, according to the above-described embodiments,the pressure of the discharged refrigerant gas introduced into therotary scroll 18 opposing the compression chamber to urge the rotaryscroll 18 toward the compression chamber and to make the axialdirectional gap of the compression chamber to be small. Furthermore, thetip seal 98 is disposed while allowing a small gap to be present in thespiral tip seal groove 98 formed at only the front portion of the rotaryscroll wrap 18a. As a result, the rotary scroll 18 is pushed toward thefixed scroll 15 by the urged pressure of the discharged refrigerant gasintroduced into the back pressure chamber 39 of the rotary scroll 18.Therefore, the enlarging of the axial directional gap of the compressionchamber is prevented. As a result, the tip seal 98a will assuredly sealthe axial directional gap between the front portion of the spiral wrapof the rotary scroll 18 and the fixed scroll 15 at which the leakage ofthe compressed gas will easily occur due to the dimensional deviationdepending upon the combination of the parts of the two scrolls. Adesired small gap (substantially no gap) can be secured in the axialdirectional gap between the front portion of the spiral wrap of thefixed scroll and the rotary scroll 18. Therefore, the sealing can beperformed without the tip seal. As a result, the operation can becontinued at the normal operation while reducing the compressed gasleakage.

In a case where the pressure in the compression chamber is abnormallyexcessively raised, the rotary scroll 18 is separated from the fixedscroll 15 in the axial direction. Therefore, the axial directional gapbetween the front portion of the spiral wrap of the fixed scroll and therotary scroll 18 is enlarged, causing the refrigerant gas leak in thecompression chamber to be generated instantaneously. Therefore, thepressure in the compression chamber can be rapidly lowered, causing thecompression load to be reduced. As a result, the durability of thecompressor can be improved.

(2) According to the above-described embodiments, the rotary scroll 18is disposed between the body frame 5 and the fixed scroll 15 whilekeeping the axial directional gap. Furthermore, the thrust bearing 20receiving the back side urging force toward the rotary scroll 18 byutilizing the pressure of the compressed refrigerant gas and disposedbetween the rotary scroll 18 and the body frame 5 acts to allow, by asmall quantity, the maximum movable gap in the axial direction in whichthe oil film can be formed between the rotary scroll 18 and the fixedscroll. In a case where the thrust load acting due to the pressure ofthe compression chamber is larger than the back side urging force actingon the thrust bearing 20, the fact that the rotary scroll 18 isseparated from the fixed scroll in the axial direction and retractingwhile pushing the thrust bearing 20 is allowed. Thus, the axialdirectional gap between the rotary scroll 18 and the fixed scroll 15 isenlarged. Furthermore, the compressed refrigerant gas to be introducedto the back side of the thrust bearing 20 is arranged to be introducedfrom the space in the final compression stroke of the compressionchamber. Therefore, the pressure of the compressed refrigerant gas to beintroduced into the back side of the thrust bearing 20 which supportsthe rotary scroll 18 at its portion opposing the compression chamber hasnot been raised at the time of the start of the compressor. When therotary scroll 18 is separated from the fixed scroll by the pressure ofthe compression chamber and the pressure in the compression chamber islowered due to the leakage of the compressed refrigerant gas from thecompression chamber, causing the starting load to be reduced.

After the operation of the compressor has been commenced, therefrigerant gas which has been compressed completely can be introducedinto the back side of the thrust bearing 20. As a result, the rotaryscroll 18 can be supported by the thrust bearing 20 and the axialdirectional gap of the compression chamber can be retained to a smallextent. Therefore, the operation can be started while realizing anexcellent compression efficiency and reducing the compressed gas leakageat an early stage after the start of the compressor.

(3) According to the above-described embodiments, the rotary scroll 18is disposed between the body frame 5 and the fixed scroll 15 whilekeeping the axial gap. The thrust bearing 20 arranged to receive theback side urging force toward the rotary scroll 18 by utilizing thepressure of the compressed refrigerant gas and disposed between therotary scroll 18 and the body frame 5 allows the rotary scroll 18 tohave a small degree of the axial directional maximum movable gap withwhich the oil film can be formed between the rotary scroll 18 and thefixed scroll 15. Therefore, when the thrust load acting due to thepressure of the compression chamber is larger than the back side urgingforce acting on the thrust bearing 20, the fact that the rotary scroll18 separates from the fixed scroll in the axial direction and retractswhile pushing the thrust bearing 20 is allowed. Furthermore, the axialdirectional gap between the rotary scroll 18 and the fixed scroll 15 isarranged to be enlarged. Furthermore, the compressed refrigerant gas tobe introduced to the back side of the thrust bearing 20 is arranged tobe introduced from compression chamber allowed to communicate with thedischarge chamber 2 and the throttle path is formed at the intermediateposition of its introduction path (the thrust back pressure introductionhole 89a and the thrust back pressure introduction hole 89b). Therefore,the pressure of the refrigerant gas, which has been completelycompressed, to be introduced to the back side of the thrust bearing 20which supports the rotary scroll 18 at its portion opposing thecompression chamber is reduced at the intermediate position of itsintroduction path so as to reduce the back pressure urging force actingon the thrust bearing 20. As a result, the rotary scroll 18 is separatedfrom the fixed scroll 15 by the pressure of the compression chamber,causing the refrigerant gas in the compression chamber to be leaked. Asa result, the low load start of the operation can be performed. With thelapse of time after the start, the pressure of the refrigerant gasintroduced into the back side of the thrust bearing 20 is graduallyraised. Therefore, the back pressure urging force acting on the thrustbearing is gradually enlarged. Then, the rotary scroll can be supportedby the thrust bearing 20 and the small axial directional gap of thecompression chamber can be gradually retained. As a result, theoperation can be gradually shifted to the full load operationsimultaneously with the start of the supply of the lubricating oil tothe sliding portions after the start of the operation.

As a result, the rapid load change in the initial stage at the start ofthe operation of the compressor can be prevented and the generations ofthe vibration and noise at the initial stage of the start of theoperation can be prevented. In addition, the durability of thecompressor can be improved.

INDUSTRIAL APPLICABILITY

As described above, the structure is arranged in such a manner that therotary scroll is urged toward the compression chamber by utilizing thepressure of the compressed fluid introduced into the rotary scroll inthe portion opposing the compression chamber to retain the small axialdirectional gap of the compression chamber. Furthermore, the seal memberis disposed while allowing the small gap in the spiral groove formed atonly the front portion of the rotary scroll wrap. As a result, theurging pressure of the discharged fluid introduced into the backpressure chamber of the rotary scroll is used to push the rotary scrolltoward the fixed scroll so that the enlargement of the axial directionalgap of the compression chamber is prevented. As a result, the sealmember will assuredly seal the axial directional gap between the frontportion of the spiral wrap of the fixed scroll and the rotary scroll atwhich the leakage of the compressed gas will easily occur due to thedimensional deviation depending upon the combination of the parts of thetwo scrolls. Therefore, a desired small gap (substantially no gap) canbe secured in the axial directional gap between the front portion of thespiral wrap of the fixed scroll and the rotary scroll. Therefore, thesealing can be performed without the tip seal. As a result, theoperation can be continued at the normal operation while reducing thecompressed gas leakage.

In a case where the pressure in the compression chamber is abnormallyexcessively raised, the rotary scroll is separated from the fixed scrollin the axial direction. Therefore, the axial directional gap between thefront portion of the spiral wrap of the fixed scroll and the rotaryscroll is enlarged, causing the refrigerant gas leakage in thecompression chamber to be generated instantaneously. Therefore, thepressure in the compression chamber can be rapidly lowered, causing thecompression load to be reduced. As a result, the durability of thecompressor can be improved.

The second invention is constituted in such a manner that the rotaryscroll is disposed between the stationary member for fixing the fixedscroll and the fixed scroll while maintaining the axial directional gap.Furthermore, the thrust bearing receiving the back side urging forcetoward the rotary scroll by utilizing the pressure of the compressedfluid and disposed between the rotary scroll and the stationary memberallows the rotary scroll to have a small maximum axial directionalmovable gap with which the oil film can be formed between the rotaryscroll and the fixed scroll. As a result, in a case where the thrustload acting due to the pressure of the compression chamber is largerthan the back side urging force acting on the thrust bearing, the factthat the rotary scroll separates from the fixed scroll in the axialdirection and retracts while pushing the thrust bearing is allowed. As aresult, the axial directional gap between the rotary scroll and thefixed scroll is enlarged. Furthermore, the compressed fluid to beintroduced into the back side of the thrust bearing is introduced fromthe space in the final compression stroke of the compression chamber. Asa result, the pressure of the compressed gas to be introduced into theback side of the thrust bearing which supports the rotary scroll in theportion opposing the compression chamber is not raised at the time ofthe start of the compressor. In addition, the rotary scroll is separatedfrom the fixed scroll by the pressure of the compression chamber tocause the compressed gas in the compression chamber to leak. As aresult, the pressure in the compression chamber is reduced so that theload at the start of the operation can be reduced.

Furthermore, after the start of the operation of the compressor, the gaswhich has been completely compressed can be introduced into the backside of the thrust bearing. As a result, the rotary scroll can besupported by the thrust bearing and the small axial directional gap ofthe compression chamber can be retained. Therefore, the operation whileexhibiting an excellent compression efficiency can be started at theearly stage after the start of the compressor.

The third embodiment is constituted in such a manner that the rotaryscroll is disposed between the stationary member for fixing the fixedscroll and the fixed scroll while retaining an axial directional gap.Furthermore, the thrust bearing receiving the back side urging forcetoward the rotary scroll by utilizing the pressure of the compressedfluid and disposed between the rotary scroll and the stationary memberallows the rotary scroll to have a small maximum axial directionalmovable gap with which the oil film can be formed between the rotaryscroll and the fixed scroll. As a result, in a case where the thrustload acting due to the pressure of the compression chamber is largerthan the back side urging force acting on the thrust bearing, the factthat the rotary scroll separates from the fixed scroll in the axialdirection and retracts while pushing the thrust bearing is allowed. As aresult, the axial directional gap between the rotary scroll and thefixed scroll is enlarged. Furthermore, the compressed fluid to beintroduced into the back side of the thrust bearing is introduced fromthe compression chamber allowed to communicate with the dischargechamber. Furthermore, a throttle path is formed at an intermediateposition of the introduction path. Therefore, the gas which has beencompletely compressed and to be introduced into the back side of thethrust bearing which supports the rotary scroll in its portion opposingthe compression chamber at the initial stage of the start of theoperation of the compressor is reduced in pressure at an intermediateposition of the introduction path. Therefore, the back pressure urgingforce acting on the thrust bearing is reduced so as to separate therotary scroll from the fixed scroll by the pressure of the compressionchamber. As a result, gas in the compression chamber is leaked so thatthe low load start operation can be performed.

With the lapse of time after the start of the operation, the pressure ofthe compressed gas introduced into the back side of the thrust bearingis gradually raised and the back pressure urging force acting on thethrust bearing is gradually enlarged. Then, the rotary scroll can besupported by the thrust bearing and the small axial directional gap ofthe compression chamber can be retained. As a result, the operation canbe gradually shifted to the full load operation simultaneously with thestart of the supply of the lubricating oil to the sliding portion afterthe start of the operation.

As a result, the rapid load change at the initial stage of start of thecompressor can be prevented and the vibration and noise at the initialstage of the start of the operation can be prevented. In addition, thedurability of the compressor can also be improved.

What is claimed is:
 1. A scroll compressor comprising:a fixed scrollhaving a first wrap support disk and a first spiral scroll wrap thereon,said first spiral scroll wrap having a forward end; an orbital scrollhaving a second wrap support disk and a second spiral scroll wrapthereon, said fixed scroll and said orbital scroll being disposed todefine a compression chamber therebetween, said second spiral scrollwrap having a forward end; means for causing said orbital scroll toorbit relative to said fixed scroll to reduce a volume of saidcompression chamber to compress a fluid in said compression chamber; andan elastic seal member disposed in the forward end of only a first oneof the first spiral scroll wrap and the second spiral scroll wrap, saidelastic seal member contacting a second one of said first wrap supportdisk and said second wrap support disk; said forward end of said secondone of said first spiral scroll wrap and said second spiral scroll wrapdirectly facing said first one of said first wrap support disk and saidsecond wrap support disk.
 2. A scroll compressor according to claim 1,wherein the fixed scroll further has a bearing surface on said firstwrap support disk for supporting the orbital scroll thereon, the forwardend of the first spiral scroll wrap faces directly to the orbitalscroll, and the forward end of the first spiral scroll wrap and thebearing surface extend on a plane.